os?. :■■.■:■/ 3 ; * // UNITED STATES DEPARTMENT of COMMERCE MARITIME ADMINISTRATION U. S. DEPARTMENT OF COMMERCE Maurice H. Stans, Secretary Rocco C. Siciliano, Under Secretary MARITIME ADMINISTRATION Andrew E. Gibson, Administrator RADAR INSTRUCTION HANDBOOK U.S. DEPARTMENT OF COMMERCE MARITIME ADMINISTRATION JULY 1969 CONTENTS PAGE ACKNOWLEDGEMENT I FOREWORD II CHAPTER 1 - INTRODUCTION TO RADAR Section 1.1 - History Of Radar 1-1 Section 1.2 - Radar And Collision Prevention 1-7 CHAPTER 2 - PRINCIPLES OF RADAR Section 2.1 - Basic Radar Theory 2-1 Section 2.2 - Resolution 2-7 Section 2.3 - The Radar Pulse 2-9 Section 2.4 - Minimum Range 2-11 Section 2.5 - Questions 2-15 CHAPTER 3 - INTERPRETATION OF RADAR Section 3*1 - Radar And Collision Avoidance 3-1 Section 3.2 - Effect Of Weather On Radar 3-4 Section 3.3 - The Effect Of Target Character- istics 3-6 Section 3-^ - Radar Navigation 3-8 CHAPTER 4 - OPERATION OF RADAR SETS Section 4.1 - Primary Radar Controls 4-1 Section 4.2 - Operating Procedures 4-2 Section 4.3 - Maintenance And Safety Precautions 4-23 PAGE CHAPTER 5 - INTERNATIONAL RULES OF THE ROAD - RADAR Section 5.1 - Review Of Rules Of The Road 5-1 Section 5.2 - Annex To The Rules 5-7 Section 5° 3 - Avoiding Collision In Restricted Visibility 5-9 CHAPTER 6 - FUNDAMENTALS OF RADAR PLOTTING Section 6.1 - Maneuvering Board H.O. 2665, Series 6-1 Section 6.2 - Logarithmic Time, Speed And Distance Scale 6-5 Section 6.3 - Time, Speed And Distance Problems 6-8 Section 6.4 - Maneuvering Board Symbols 6-10 Section 6.5 - The Relative Motion Plot 6-11 Section 6.6 - Maneuvering Board Procedure, (Speed Vector Diagram) 6-17 Section 6.7 - Maneuvering Board Problems 6-19 CHAPTER 7 - RAPID RADAR PLOTTING Section 7*1 - Development Of Rapid Radar Plotting 7-1 Section 7.2 - Radar Plotting Sheet - 4665 Series_ 7-6 Section 7.3 - Distance Triangle Method "A" 7-8 Section 7-4 - Distance Triangle Problems - Method "A" 7-17 Section 7.5 - Distance Triangle - Method "B" 7-20 Section 7»6 - Distance Triangle Problems - Method "B" 7-27 Section 7„7 - True Motion 7-35 CHAPTER 8 - DIRECT/REFLECTION PLOTTING Section 8.1 - Tools And Equipment 8-1 Section 8.2 - Reflecting Plotting 8-4 PAGE CHAPTER 9 - RADAR SIMULATORS Section 9*1 - Development Of Marine Radar Simulators 9-1 Section 9.2 - Use Of Radar Simulators 9-7 APPENDICES Appendix A - Glossary 10-1 Appendix B - Emergency Shiphandling Information 10-5 Bibliography 10-9 ACKNOWLEDGEMENT The purpose of this Handbook is to bring to the merchant marine officer a treatise on radar that will serve as a complete ref- erence book with which to maintain intelligent radar usage in collision avoidance. This publication is the result of the efforts of many individuals. It had the advantage of drawing on numerous excellent studies and publications listed in the Bibliography as well as the latest course material used by MarAd instructors and others. The Maritime Administration acknowledges with sincere appreciation the contributions of the following qualified authorities from other agencies whose review and critique contributed substantially to this publication: Admiral L. M„ Thayer, USCG (Ret. ), National Transportation Safety Board; Captain M. Foreman, USCG (Ret.), MSTS Headquarters; Cdr. E. F. Oliver and Cdr. S. J. Dasovich, USCG Headquarters; Mr. Ernest Brown, U. S. Naval Oceano- graphic Office; CW4 Carter James and Mr. Snodgrass, U, So Army Transportation Training Command, Marine Division. The preliminary technical review and assembly of the working draft was performed by Mr. William Eo Poehl, Jr., MarAd, New Orleans. Mr. Pierre R. Becker, Chief, Division of Manpower Development, carried the basic responsibility for coordinating all efforts toward production of this publication. Office of Maritime Manpower Maritime Administration FOREWORD One of the most promising navigational aids for the avoidance of collisions at sea was the invention of radar almost twenty- five years ago. Yet in spite of glowing predictions of a new era of safety at sea, collisions have continued to cause heavy damage and loss of life year after year. It became evident that radar was not being properly used as an anti- collision device through proper plotting to evaluate the information provided by the radar, so that a safe course of action could be indicated to avoid collision. The Maritime Administration has for some years conducted radar simulator classes in three radar observer schools, where ship officers are given a chance to study and exercise their skills in plotting and maneuvering under simulated sea conditions. This new manual has been prepared to complement this program and to present the most effective present day plotting techniques. It is the responsibility of the radar operator to make use of what he has learned when he returns to his ship. Upon his care and skill rests much of the reputation of U.S. merchant ships for being among the safest in the world. ison Maritime Administrator II CHAPTER 1 INTRODUCTION TO RADAR Section 1.1 HISTORY OF RADAR Radar is a radiation device which may "be used for detection and ranging of targets independent of time and weather conditions. It is properly studied under communications since it extends one of the senses of the navigator- -that of sight. It furnishes him with intelligence by permitting him to see some object that is not visible. The word "radar" is derived from the phrase RAdio Detection And Ranging. Undoubtedly, radar was one of the greatest scientific developments which emerged from World War II. Its development, like that of most other great inventions, was mothered by necessity—in this case, the necessity for offsetting an offensive weapon which made its first appearance in World War I, the military airplane. The basic principles upon which its func- tionings depend are simple and easily understood. Therefore, the seem- ingly complicated series of electrical events encountered in radar may be resolved into a logical series of functions. Although the complete history of the origin and growth of modern radar is long and complicated, it is of sufficient interest to sketch here its main points. Successful pulse-radar systems were developed independently in America, England, France, and Germany during the latter part of the 1930' s. Behind the development lay more than fifty years of radio development 1-1 for communication purposes, and a few early suggestions that, since radio waves are known to be reflected by objects whose size is in the order of a wavelength, they might be used to detect objects in fog or darkness. The fact that radio waves have optical properties identical with those of light was established by Heinrich Hertz in 1886 in the famous series of experiements in which he first discovered radio waves. Hertz showed, among other things, that radio waves were reflected by solid objects. In 190^-, a German engineer, Hulsmeyer, was granted a patent in several countries on a proposed way of using this property in an obstacle detector and navigational aid for ships. In 1922, Marconi strongly urged the use of short waves for radio detection. One of the first observations of radio echoes was made in the United States in 1922 by Dr. Albert H- Taylor of the Naval Research Laboratory. Taylor observed that a ship passing between a radio transmitter and re- ceiver reflected some of the waves back toward the transmitter. By 1930 further tests proved the military value of this principle for the de- tection of surface vessels which were hidden by smoke or darkness. Further developments were conducted with carefully guarded secrecy. During this same period, Dr. Breit and Dr. Tuve of the Carnegie Institute at Washington published a report concerning their investigations of the ionosphere in which they first employed the principle of pulse ranging for measuring the height of the ionosphere. It is this principle which characterizes modern radar. After the successful experiments of Breit and Tuve, the radio-pulse echo technique became the established method for ionospheric investigation in all countries. In retrospect, the step from this technique to the idea of employing it for the detection of 1-2 aircraft and ships is not a great one. The application was evolved by various individuals, acting independently and almost simultaneously in America, England, France, and Germany about ten years after the original work by Breit and Tuve. The United States military research agencies have a long history of early experiment, total failure, and qualified success in the field of radio detection. In early 1939> a radar set designed and built by the Naval Research Laboratory was given exhaustive tests at sea during battle maneuvers. Earlier, in November 1938^ a radar position-finding equipment intended for the control of antiaircraft guns and search- lights, was designed and built by the Signal Corps _ Laboratories. This set underwent extensive tests and then went into production and became known as the SCR-268. The Air Force requested the Signal Corps to design and construct a long-range radar for the detection of aircraft. This set was successfully demonstrated in November 1939* with actual large-scale production getting underway in August 19^-0. This radio equipment became known as the SCR-270. British radar was developed by about the same time but its application proceeded at a somewhat faster rate because of the pressure of war. The first experimental radar system of the type suggested by Sir Robert Watson-Watt was set up in the spring of 1935 on a small island off the coast of England. Development work during the summer led to the blocking out of the main features of the British early-warning stations by fall. Work began in 1936 toward setting up five stations about twenty- five miles apart to protect the Thames estuary. By March 1938, all these stations, the nucleus of the final chain, were complete and in operation. 1-3 British radar development then turned its maximum efforts to airborne equipment. Two types were first envisioned; a set for the detection of surface vessels "by patrol aircraft, to he known as "ASV equipment," and an equipment for enabling night fighters to home on enemy aircraft, to he known as "AI" (Aircraft Interception). The first work was done on the ASV equipment and a successful demonstration made during fleet maneuvers in September 1938- Working models of the AI equipment were completed by June 1939 and successful demonstrations were made to the RAF Fighter Command in August. Four of these sets were installed and operating when the war broke out in September. Emphasis on airborne radar brought out clearly that if sharp radar beams were to be produced by antennas small enough to be carried on aircraft, wavelengths shorter than the 1-1/2 meters used in the early British airborne equipment would have to be employed. This naturally led to the effort of developing a generator of microwaves which could give pulse power adequate for radar use. By early 19^-0, a British version of the multi-cavity magnetron had been developed to the point where it was an entirely practicable source of pulsed microwave energy. In the fall of 19^-0, an early model of this magnetron operating on ten centimeters was brought to the United States for examination. The first American test of its power capabilities was made in October at the Bell Telephone Laboratories. This test confirmed British information and demonstrated that a generator now existed which was capable of supplying several times the power of the conventional triodes then in use and at a frequency four times greater. This point marks the beginning of modern radar. 1-1+ Multi-cavity magnetron oscillators are now available for use in pulsed and continuous -wave generators at wavelengths from .5 to 50 centimeters. The upper limits of peak power now available are approximately 100 kilowatts at 1 centimeter, and 3 megawatts at 10 centimeters. The amount of peak power available for use decreases as the wavelength is decreased but improvements in magnetron design have been steadily push- ing the amount of peak power available to higher values. Magnetrons may have operating voltages from about 1 kilovolt to k-0 kilovolts. The magnetic field essential to operation ranges from 600 to 15,000 gausses. Tunable magnetrons are now available for many portions of the microwave band. The effectiveness of radar as both an offensive and defensive weapon is already generally known, but some of the most salient features may bear repeating. The British early-warning chain of radar stations is credited with having saved that country during the German blitz warfare in late 19^-0. Its tactical employment permitted a small RAF fighter force to be used at its greatest efficiency. The radar system allowed the aircraft to remain on the ground until approaching enemy aircraft were detected, then the fighters could be sent into the air to meet the enemy. The employ- ment of an aircraft warning system of this type enabled the RAF to withstand the assaults of a numerically greater air force. If the method of maintaining aircraft on constant air patrol had been employed, it would have required many more pilots and aircraft then the British had available for the task. The use of radar permitted the planes to be 1-5 serviced and the pilots to rest during periods of inactivity. At first, radar was envisioned as a defensive weapon, but as the war progressed it came to be used for offensive purposes. By the end of May 19^-1> radar had been employed to track aircraft automatically in azimuth and elevation and later to track the target automatically in range. This was the prototype of the antiaircraft position finder. The equipment for this purpose later became known as the SCR-584 and the SCR-5^5- Farther advancement in the field of airborne radar permitted the develop- ment of sets that could be employed for long range navigation through overcast skies and the carrying out of strategic bombing missions in all kinds of weather. The technique of radar bombing was developed which permitted the bombardier to hit his target even though it was not visible to him. These developments gave the Air Force the ability to perform its job on an around-the-clock basis in all kinds of weather-- an essential feature in successful military operations. Gunfire-control radar developed as rapidly as the other types of radar. The Navy had success in destroying enemy shipping and naval forces with radar-controlled guns. However, the development of fire-control radar was not confined to surface equipment. The same principles were em- ployed in making airborne gun-laying equipment. Radar, both airborne and ground, has made a lasting impression on military tactics and will find an important place in the defense scheme of the nation and in any future military operations. Radar is employed extensively in marine navigation and may become man- datory on all foreign and domestic vessels over 1600 tons. 1-6 CHAPTER 1 - INTRODUCTION TO RADAR Section 1.2 - RADAR AND COLLISION PREVENTION Used properly, radar is a valuable aid in collision prevention. In the hands of a crew which lacks a full understanding of what it will do, and what it will not do, it may he worse than useless. It may actually contribute to the danger of collision. The radar-assisted collision is not a myth. It has occurred on more than one occasion when lack of under- standing of the limitations of radar has led to improper action, resulting in collision which might not have occurred if radar had not been available. One should keep clearly in mind the fact that radar provides an in- stantaneous indication of present distance and present direction of con- tact. It does not identify the contact as a ship or even as a moving object, nor does it, in general, directly indicate the course or speed of another vessel, or its aspect. It gives no reliable information as to the size and "cype of the contact. It provides no immediate indi- cation of a change of course or speed by another vessel. It does not reveal the intent of another vessel, or even the probable intent, because it provides no clue as to whether the other vessel is equipped with radar, whether the bridge personnel of the other vessel has sized up the situation the same as personnel of own ship, or whether the other vessel is even aware of the presence of own ship. In short, radar is not the equivalent of visual observation. Radar provides an instantaneous indication of present distance and present direction of a contact. By itself, this information is of relatively little value in avoiding collision. Supplemented by the additional 1-7 information provided by an adequate plot, if followed by intelligent action in ample time, it is capable of preventing virtually all colli- sion of radar-equipped ships on the open sea. 1-8 CHAPTER 2 - PRINCIPLES OF RADAR Section 2.1 - BASIC RADAR THEORY In the basic block diagram shown on page 2-2, it will be seen that a shipborne type radar usually consists of three major components; the Scanner, Transceiver and Indicator. SCANNER: Two types of scanners are generally employed in marine radar instal- lations. The older parabolic reflector type and the newer slotted wave guide type. The former consists of a 4', 8' or 12' parabolic reflector, drive assembly and horn which rotates between 10 and 2u R.P.M., depending on the design of the equipment. The scanner must be mounted on a mast higher than most of the ship' s superstructure in order to eliminate blind spots caused by other masts, king posts, stack, etc. Radar energy is conducted to the horn from the transmitter through a hollow rectangular pipe called a wave guide. At the end of the horn is a plastic window. The energy passes through the window and is directed toward the reflector. The reflector in turn focuses the energy into a narrow beam which is being constantly rotated. It scans the area surround- ing the ship and any object in the path of the beam reflects back that part of the energy which strikes it. The main purpose of the reflector is to concentrate the radar energy into a narrow beam which in modern radars is 0.65° in width. It is called horizontal beam width. This narrow beam provides us with good bearing resolution. 2-1 BASIC BLOCK DIAGRAM OR RADAR COMPONENTS WAVEGUIDE _£2 TR TUBE IS TRANSMITTER (MAGNETRON) RECEIVER MODULATOR TRANSCEIVER VIDEO TIMING TRIGGER INDICATOR Courtesy of Sperry Marine Systems Division 2-2 The height of the radar beam is called vertical beam width and is usually between 15 and 20 degrees. The vertical beam width permits the scanner to search an area in the immediate vicinity of the ship on out to the horizon, with sufficient height to allow for the normal rolling and pitching of a vessel. It is possible during excessive rolling and pitching for the radar beam to miss targets completely, therefore, a closer radar watch should be maintained during this time. TRANSCEIVER: The word transceiver is a contraction of the words transmitter and receiver. It will be seen in the block diagram that the transmitter and receiver are interconnected through a common wave guide with the scanner. In transmitting, the magnetron tube provides the RF energy to the scanner which was explained earlier. A TR tube located between the transmitter and receiver blocks transmitted energy to the receiver thus preventing damage to the receiver crystal component. Because the radar is a pulsed type, the magnetron will extinguish after transmitting a short burst of energy. From this moment until the magnetron again fires, the TR tube will permit the returning 'echo' signal to be received and amplified. It is then conducted through an interconnecting cable, called a co-ax, to the indicator. The modulator provides the timing of the transmitted pulses which are sent out by the magnetron. The modulator also provides the timing for starting the sweep on the cathode ray tube. This is accomplished through a second co-ax cable, which is called the trigger. INDICATOR: To the radar observer, the indicator is the most important component of 2-3 his radar, for it is this unit that provides him with the information he seeks in collision avoidance and stranding. The indicator is fitted with a Cathode Ray Tube (CRT) which can be l6 inches in diameter or more. It is on this scope that all objects which reflect radar energy are seen. This type of presentation is called Plan Position Indicator (PPl) or polar presentation. Just as in a polar diagram, the center of the scope represents your own ship. From this center a bright line emanates which sweeps toward the outer edge of the tube and is called a sweep line . This sweep is synchronized (trigger) with the number of pulses being transmitted. Therefore, if the radar were transmitting 3000 pulses per second, the scope sweep would be 3000 times per second. This speed is far in excess of what the human eye can see, and the sweep appears to be a solid rotating line. The rotation of the sweep line is synchronized with the rotating scanner. Thus if the scanner rotates 15 RPM then the sweep line rotates 15 RPM. The small amount of energy received by the antenna is detected by the receiver, amplified, ana converted into signal voltages, called video signals. The video signals are then applied to the indicator and appear on the radar scope at the range and bearing of the contacts. DETERMINATION OF RANGE: Radar waves travel in a straight line with the speed of light (approx- imately 1000 feet every microsecond). Since the velocity is constant, the time it takes the radar wave to travel to the target and back can be accurately measured. The radar scope is the measuring device. The time scale is calibrated in miles. Thus, when a signal is transmitted, the radar scope begins to time the travel of the signal. When the 2-k reflected signal is returned from the contact, a mark appears on the radar scope as a spot of light indicating the time of return. Since the time scale is calibrated in miles, the mark on the radar scope indicates range. The bearing of the target is determined by rotating the cursor until the center hair line passes through the pip (contact). The bearing is then read on the azimuth circle on the outer edge of the CRT as true bearing, provided the radar has a true bearing adaptor or is of the true bearing stabilized type. Operational controls, both primary and secondary are located on the indicator. 2-5 RCA - CRM - N2A - 30 c r ( r 83-29 Ji PHA 2760 TRANSMITTER / RECIEVER UNIT Courtesy of Radiomarine Corp. 2-6 CHAPTER 2 - PRINCIPLES OF RADAR Section 2.2 - RESOLUTION All radars are capable of resolving (distinguishing as separate) targets in "both range and bearing, but the degree of separation varies with in- dividual types and models. As an example: If two ships were close together at a range of, say 5 miles, but separated in azimuth or bearing by 1°, some radar models would not be able to distinguish these ships as two targets, instead they would appear as a single target on the CRT. On the other hand, a better radar would clearly show two separate targets on the scope. This is known as bearing resolution which is determined by the horizontal beam width. Most modern radars have a 0.65° bearing resolution. The opposite of bearing resolution is range resolution which is deter- mined in an altogether different manner. In this instance both ships would appear on the same bearing but at different ranges. The distance that these ships must be separated in range in order to appear as two separate targets on the CRT is determined by the pulse length. The shorter the pulse the better the range resolution obtained. EXAMPLES PULSE DURATION RANGE RESOLUTION .05 microsecond - 10 yards .1 microsecond - 20 yards .2 microsecond - 35 yards .25 microsecond - 55 yards The illustration on page 2-8 graphically illustrates range and bearing resolution. 2-7 RANGE AND BEARING RESOLUTION TO OBTAIN INDICATION OF TWO TARGETS, RANGE DIFFERENCE MUST BE GREATER THAN RANGE RESOLUTION OF RADAR TO OBTAIN INDICATION OF TWO TARGETS, BEARING DIFFERENCE MUST BE GREATER THAN BEARING RESOLUTION OF RADAR Courtesy of Sperry Marine Systems Division 2-8 CHAPTER 2 - PRINCIPLES OF RADAR Section 2.3 - THE RADAR PULSE In order to understand the importance of radar pulses with relation to time and the conversion of time into distance for the purpose of cali- brating the radar, it is first necessary to understand elementary char- acteristics of radio propagation. The energy that the radar transmits are radio waves, better known as RF. Radio waves travel at the speed of light or approximately l62,uo0 nautical miles per second. Consider that the earth's circumference at the equator is 21,600 nautical miles. If a radio wave could circumnavigate the earth endlessly, it would do so more than seven times in one second. With this example in mind, try to visualize how long it would take for a radio signal transmitted from your ship, to reach another vessel only 5 miles away. Obviously, it would be a very small fraction of a second. For this reason, another element of time is utilized for calculation purposes called the microsecond. A microsecond is the one millionth part of a second. Another way of expressing it is that there are 1,000,000 microseconds in one second. Now we can say that radar waves travel 162,000 nautical miles in 1,000,000 microseconds. How far will a radar wave travel in one (l) microsecond? Simply divide 1,000,000 into 162,000. - ^___^ -162 Naut. miles 1,000,000 ") 162,000. 2-9 If a radar wave will travel .162 Naut. miles in one (l) microsecond, what does this represent in yards? Simply multiply 2000 yds. (one Naut. mile) by .162. 2000 X.162 324 Naut. yards It is much easier now for us to calculate how long it would take a radar signal to travel 5 miles. 5 r -l62 = Just under 31 microseconds. Next we must consider that a radar is transmitting hursts of energy called pulses. The number of pulses transmitted in a given period of time is called PER or pulse repetition rate. Some people like to call it pulse recurrence rate. Either expression will do. The main reason why radar transmits pulses instead of continuous emission is the unique construction of the equipment. We have one scanner or antenna for both transmitting and receiving. While the radar is transmit- ting it can not receive. Therefore, the transmitter must be shut off while the receiver is in the listening condition. 2-10 CHAPTER 2 - PRINCIPES OF RADAR Section 2.k - MINIMUM RANGE It is most important that a radar be capable of detecting targets close aboard. The closest distance that objects can be seen on the radar scope is called minimum range. Let us take for example a radar that has a transmission time (pulse duration) of one (l) microsecond. We know that this represents a distance of 32^- yds. of travel. Theoretically if a target was l62 yards away from your ship, the signal would travel this distance, bounce off the target and be reflected back 162 yds. to the scanner, having travelled a total distance of 32^4- yds. At this moment the transmitter would shut off and the radar would be in a condition to receive the reflected signal. In this instance, we can see that any echoes of targets closer than l62 yds. would not be received. Therefore, the minimum range would be l62 yards. Consider another aspect of the above. If the pulse duration were l/lO (.1) of a microsecond instead of one (l) microsecond, then the minimum range would be l/lO of 162 yards or 16.2 yards. Obviously the smaller minimum range is more desirable. From the foregoing it can be seen how the pulse length also determines range resolution. The shorter the pulse, the smaller the minimum range and range resolution. The number of pulses transmitted per second also varies with different makes and models and most modern radars have two pulse repetition rates. 2-11 On short ranges (l to 6 miles) a greater number of pulses are transmitted because of the short time duration of the pulse. On long ranges (over 6 miles) fewer pulses are transmitted, but the pulse duration is usually four times as long. Sperry MK 3 Radar R.C.A. CR 1C4 R.C.A. CRM-N2C-30 Raytheon-Mar iner s Pathfinder EXAMPLES PRR 3000 PPS 750 pps 2000 PPS 8oo pps 2000 PPS 1000 PPS 1600 pps 8oo pps PULSE DURATION 0.1 microsecond O.k microsecond 0.25 microsecond O.65 microsecond 0.1 microsecond O.k microsecond 0.2 microsecond O.k microsecond FREQUENCY AND WAVELENGTH The Federal Communications Commission has alloted for commercial marine radar use, the following frequencies: X Band: Frequency 9375 + ^5 m/c - Wavelength 3-2 c/m S Band: Frequency 3070 + 50 m/c - Wavelength 10 c/m It will be noted that the higher frequency has the shorter wavelength while conversely the lower frequency has a longer wavelength. Both frequencies are used to an almost equal degree some preferring the 3 centimeter radar while others prefer the 10 centimeter. However, operational wise, it is mostly a matter of personal choice. The easiest way for the student to detect a 3 c/m radar from a 10 c/m is to examine the wave guide. 10 c/m wave guide is about the size of a 2 x k while a 3 c/m wave guide is much smaller, about l/3 the size. 2-12 EFFECTIVE RADAR RANGE Radar waves travel in almost a straight line and is commonly referred to as line of sight. The distance at which we could conceivably pick up targets is determined for the most part by height of eye, that is to say, the height of the scanner above the water and additionally, the height of the object we are observing above water. This distance can be calculated to a fairly accurate degree by consulting table eight, in the American Practical Navigator (Bowditch ) . Lower frequency radar waves will, to some extent, bend with the curvature of the earth thus increasing the radar range a small amount. Other factors must be considered though, before jumping to the conclusion that a 10 c/m radar is superior in this respect. Antenna design is one example and more important is RF power output. This is known as peak power/average power. In determining the good versus the poor qualities of any radar type, it is a simple matter to consult the manufacturer's list of technical characteristics or specifications usually published in the individual radar handbooks or instruction books. Bear in mind that just because a radar indicator boasts of a k-0 or 50 mile range scale it does not mean the unit will pick up ships at that range. It is quite possible, this same unit will have a useful maximum range of only 10 to 15 miles with regard to anti-collision observations. 2-13 REFRACTION There are two kinds of refraction that affect radar range: 1. Super- refraction is a bending of the radar beam in conformity with the earth's curvature, which increases the radar range above normal. 2. Sub -refraction is a bending of the radar beam in opposition to the the earth' s curvature which produces a decrease in the radar range from normal. Both conditions are caused by changes in the temperature and relative humidity of the earth's atmosphere. 2-l4 CHAPTER 2 - PRINCIPLES OF RADAR Section 2.5 - QUESTIONS 1. What does the word radar mean? 2. What is the velocity of radar waves? 3- What is meant by bearing resolution? h. What is meant by range resolution? 5- What does the magnetron in the transceiver do? 6. Name the major components of the radar. 7- How far would a radio wave travel in one microsecond? 8. What determines effective radar range? 9- Explain super and sub -refraction as it applies to radar waves. 10. What controls would you adjust if heavy sea return is present? 11. Give the two pulse repetition rates for the R.C.A. - CRM-N2C-30 radar, 12. How would you determine if your radar had blind spots? 13. If a vessel's radar had blind spots how would you attempt to over- come this? 1^. What wavelengths are used for marine type radars? 15. Match the correct frequency with the above wavelengths. 2-15 l6. What is vertical beam width? 17- What is horizontal beam width? 18. Describe wave guide and explain its purpose. 19- What are the two common types of scanners used for shipboard radar? 20. Explain the function of the TR tube. 2-16 CHAPTER 3 - INTERPRETATION OF RADAR Section 3.1 - RADAR AND COLLISION AVOIDANCE The Mariner must learn to properly interpret the presentation given on the CRT of the indicator. He must be aware that the display may be subject to mechanical and electronic phenomena which could give rise to faulty interpretations. Some of these are reviewed as follows: BLIND AND SHADOW SECTORS: Blind and shadow sectors may be caused by placing the ship's radar antenna in such a position that the stack, masts or other ships' structural members interfere with giving the antenna a clear 3^0° horizon. Although radar waves will bend slightly around the obstruction, the above situation may produce a shadow sector where the intensity of the return echoes is greatly reduced , If the interfering structual member is close to the antenna and sufficiently large in azimuth, it may produce a totally blind sector from which no return will be found. MULTIPLE ECHOES: Multiple echoes may be found where a large vessel passes close by your own ship. The radar pulse bounces back and forth between the two ships causing several echoes to appear on the CRT. The true contact will appear at the closest range and will be clearer and better defined. The remaining echoes will be spaced equidistantly on the same bearing at multiples of the true range, weakening in intensity as the range increases. These echoes may be minimized by proper use of the gain or clutter controls. INDIRECT ECHOES: An indirect echo may be caused by the reflection of a pulse off the stack, 3-1 mast, or other structural member. The return echo will normally appear at about the same range as the true target and often appear in an area where there is normally a blind or shadow sector. This is because the same interfering member which creates the blind sector will act as a reflector for the indirect echo. MULTIPLE TRACE ECHOES: Under certain abnormal weather conditions, radar echoes may be returned from objects beyond the normal range scale of the set. The returning echo (usually of land) arrives back after a subsequent trace has com- menced and will appear at a range where no target is expected. Changing the range scale will make the echo either appear at a different range or the echo may not appear at all. SIDE LOBE EFFECT: Most older antennas allow a certain amount of energy to "spill" out from either side, although the main force of the beam is focused in a narrow arc. This "spillage" causes two minor beams to be sent out in addition to the major beam. Echoes may be returned by these minor beams or lobes from nearby targets. These unwanted returns will appear at the same range as the true target. They may appear as small arcs at different bearings or produce a continuous ring. Their effect may be reduced by use of the STC or anti-clutter controls or by reducing the gain. The greater use today of the slotted waveguide antenna has greatly reduced the occurence of this phenomenon. INTERFERENCE: Interference is caused from the reception by the antenna of pulses sent out by another set, when these pulses are the same frequency as your own. 3-2 The STC and FTC controls may be used to suppress some interference. Inter- ference usually takes the form of either a large number of bright pips scattered about or appears as spokes from the center of the CRT. 3-3 CHAPTER 3 - INTERPRETATION OF RADAR Section 3.2 - EFFECT OF WEATHER ON RADAR Weather has a dual effect on radars' effectiveness; first it may produce reflections, and secondly it may affect the propagation of the radar pulse. WIND: The action of the wind will produce waves on the ocean surface. The vertical surfaces of the waves in turn will return an echo which may be seen on the CRT and is known as sea return. Sea return will normally be greater in the direction from which the wind and seas are coming. Sea return effects may be reduced by the proper use of STC or Anti-Clutter Controls; however care must be taken not to lose any targets in the process. PRECIPITATION: Rain, hail and snow storms all may return echoes which will show up on the CRT as a blurred or cluttered area. The FTC Control is used to minimize precipitation returns so as to reveal any targets which may have been hidden in the clutter. In addition to masking targets which are within the storm area, heavy precipitation may absorb some of the strength of the pulse and decrease maximum detection range. UNUSUAL PROPAGATION CONDITIONS: Normally we think of radar waves as being a line of sight transmission. However, similar to light waves, radar waves going through the earth' s atmosphere are subject to refraction and bend slightly with the 3-^ curvature of the earth. Certain atmospheric conditions will produce a modification of this normal refraction. SUPER -REFRACTION: This phenomenon may occur in calm weather with no turbulence where there is an upper layer of warm dry air over a surface layer of cold moist air. This occurs often in the tropics where a warm land breeze blows over cooler ocean currents. The effect of super-refraction is to increase the bending of the radar wave and thus increase the range from which echoes may be returned. DUCTINC: In some abnormal circumstances, the upper warm air layer may make sharp temperature break with the lower air. When the inversion layer or warm reflecting layer is at certain heights, a condition similar to a giant wave guide is formed and the radar wave is trapped within it. Under these rare circumstances echoes have been returned from targets over a thousand miles distant as multiple trace echoes. SUB-REFRACTION: In areas where there is a cold moist layer of upper air over warm dry surface air, sub-refraction may occur. Here radar waves tend to bend away from the earth. This causes a reduction in maximum range. More importantly to the navigator, this condition also affects minimum range and may result in the loss of small close by targets. The condition may be found in polar regions where cold air masses move over warm ocean currents. 3-5 CHAPTER 3 - INTERPRETATION OF RADAR Section 3-3 - THE EFFECT OF TARGET CHARACTERISTICS There are several characteristics which will enable one target to be picked up at a greater range than another, or for one target to produce a stronger echo than another target of similar size. Since radar waves are more or less a line of sight transmission, the height of the target is of prime importance. The following character- istics mast also be considered: ASPECT: Aspect refers to the angle of the reflecting surface to the radar beam - this may change as the ship moves. The nearer this angle is to 90°, the greater the strength of the return echo. Due to the movement of your ship and the target, aspect will change as your relative position changes. SHAPE: As opposed to aspect, the shape of the target will remain the same. Targets of identical shapes may give echoes of varying strength, depending on aspect. Thus, a flat surface at right angles to the radar beam such as the side of a ship or a cliff along the shore, will reflect very strong echo pulses. As the aspect changes, a flat surface will tend to reflect more of the energy of the beam away from the receiver, and may give rather weak echoes. A concave surface will tend to focus the radar beam back to the receiver while a convex surface will tend to scatter the energy. TEXTURE: The texture of the target may modify the effects of shape and aspect. A smooth texture tends to increase the reflection qualities, and will increase the strength of the reflection, but unless the aspect and shape of the target are such that the reflection is focused directly back to the sender, the smooth surface will give a poor radar echo since most of the energy is reflected in another direction. On the other hand, a rough surface will tend to break up the reflection, and will improve the strength of return echoes from those targets whose shape and aspect normally give weak return echoes. COMPOSITION: The ability of various substances to reflect radar pulses depends on the intrinsic electrical properties of that substance. Thus metal and water are good reflectors. Ice is a fair reflector, depending on aspect. Land areas vary in their reflection qualities depending on the amount and type of vegetation and the rock and mineral content. Wood and fibre glass boats are poor reflectors. It must be remembered that all four of the characteristics interact with each other to determine the strength of the radar echo and no factor can be singled out without considering the effect of the others. 3-7 CHAPTER 3 - INTERPRETATION OF RADAR Section 3.k - RADAR NAVIGATION Radar provides ranges and bearings of known objects and in doing so, provides the Observer with an additional tool in establishing position. However, there are certain pitfalls which must be avoided. RADAR RANGES: The range accuracy of most marine radars is excellent, but problems may be encountered trying to identify objects on the PPI and locate them on the chart. Small objects such as isolated rocks, light- ships and buoys provide the best contacts because they are easy to identify. Care must be taken to avoid false shorelines, these may be caused by heavy surf or reefs, offshore rocks, fishing boats, etc. On the other hand, cliffs or sand dunes in back of a beach may be shown and the low shoreline of the beach may not appear at all. RADAR BEARINGS: Radar bearings are not as accurate as radar ranges. In addition, they are subject to the same limitations in regard to the difficulty of determining the identification of an echo with the corresponding point on the chart. Due to beam width, tangent bearings are subject to an inherent error. Therefore, when taking tangent bearings, a correction equal to one half of the beam width must be applied to obtain the correct bearing. No correction is needed for bearings taken from the center of an object. 3-8 AIDS TO RADAR NAVIGATION: To aid the Observer in locating or identifying a contact, certain aids to radar navigation have "been developed. These include: RADAR REFLECTORS: Are used to produce a strong echo from an object that would normally give a weak return, such as buoys or small wooden boats. Tney are a passive aid and usually consisting of several light metal planes at angles to each other. RAMARK: Is a radar signal continuously transmitted by a shore station independent of the ship. It produces a pattern of dots or dashes in a line from the center of the scope. These identify the station and serve to indicate the station' s bearing from your ship. RACON: Is a radar signal transmitted by a shore station when triggered by a pulse transmitted by a ship's radar. It transmits a coded signal of dots and dashes from which the identity of the station is determined through both range and bearingo 3-9 CHAPTER k - OPERATION OF RADAR SETS Section k.l~ - PRIMARY RADAR CONTROLS The following are considered to be the main or primary controls and are used on most equipment: 1. Range Scale Switch - Used to change ranges from 1 to 40 miles. 2. Variable Range Marker - Used to facilitate obtaining range in- formation. The results will read on a veeder counter. 3- Receiver Gain - Adjusts sensitivity of radar receiver. h. Cursor - Adjusts movable cross-hair to obtain bearings of contacts. 5- True and Relative Bearings - Changes presentation from true to relative bearing. On some sets also adjusts outer azimuth scale to heading in order to obtain true bearings. 6. Anti-Clutter Controls - To minimize the effects of sea return and rain clutter. 7- Suppressor - Designed to suppress sea return. Care should be used not to advance control too far clockwise as close in contacts may be lost. 8. STC Gain - Designed to suppress sea return. Usually adjustable from to 8 miles. Care should be used not to advance this control too far counter-clockwise as close in contacts may be lost. 9- FTC-On - Designed to minimize the effects of rain clutter and beam k-1 down large masses. Under certain conditions both STC Gain and FTC can be used to good advantage. 10. Video - Brightens contacts and background. To be used in conjunction with Gain Control. 11. Lin-Log (Sperry) - Designed to suppress sea return. Log position, during periods of excessive sea return 1, 2 and 6-mile ranges. Lin position 15 and 40-mile ranges. When Log position is used, Gain Control should be advanced until sweep sprinkles appear. 12. Ant i- Clutter - Used to minimize the effects of sea return. and rain clutter: Position 1 - calm sea Position 2 - calm and rain Position 3 - rough sea Position k - rough and rain k-2 CHAPTER h - OPERATION OF RADAR SETS Section 4.2 - OPERATING PROCEDURES THERE IS AT PRESENT A VARIETY OF RADAR TYPES AND DESIGNS CURRENTLY BEING USED ABOARD AMERICAN FLAG VESSELS. SINCE SPACE DOES NOT PERMIT A COMPLETE DISSERTATION ON OPERATIONAL PROCEDURES FOR EVERY TYPE OF RADAR IN USE TODAY, THE FOLLOWING OPERATIONAL PROCEDURE APPLIES ONLY TO THE R.M.C.A., CRM-N2C-30, 10 CM RADAR. IF YOU ARE KNOWLEDGEABLE IN THE OPERATION OF ANY ONE OR SEVERAL TYPES OF RADAR, THE TRANSITION TO OPERATING OTHER TYPES SHOULD BE ACCOMPLISHED WITH EASE. NORMALLY YOU WILL FIND AT LEAST ONE COPY OF AN OPERATOR'S INSTRUCTION BOOK ON THE BRIDGE OR IN THE CHART ROOM OF YOUR SHIP, WHICH WILL PROVIDE YOU WITH FIRST-HAND INFORMATION REGARDING THE OPERATIONAL PROCEDURE OF THE INDIVIDUAL RADAR EQUIPMENT WHICH YOU WILL BE USING. h-3 RCA - CRM - N2C - 30 RELATIVE /TRUE SEARING DISPLAY SWITCH PLOTTER DIMMER RANGE INDICATORS VARIABLE RANGE MARKER COUNTER AND CONTROL BEARING CURSER CONTROL FLASHER INTENSITY CONTROL PANEL ECHO BOX CONTROL SWITCH VARIABLE FIXEO RANGE MARK RANGE MARK FTC INTENSITY INTENSITY SWITCH CONTROL CONTROL 8027083-14 INDICATOR, OPERATING CONTROLS Courtesy of Radiomarine Corp. k-k RCA - CRM - N2A - 30 . ■ 93283 PHB2508 8027085-24 RELATIVE MOTION INDICATOR WITH REFLECTION PLOTTER Courtesy of Radioraarine Corp. U-5 TYPICAL OPERATIONAL PROCEDURE (R.M.C.A., CRM-N2C-30, 10 CM RADAR) RELATIVE MOT IO N INDICATOR General All operating controls for the radar are located on the indicator unit. The purposes of each control, and descriptions of their operating func- tions and proper adjustments, are given below. Efficient operation of the radar will be attained by understanding the function of each control, and by close observation of the CRT indicator when making adjustments. DI SPLAY TUBE (CRT OR "SCOPE") The scope tube is 16 inches in diameter and displays a large, easily viewed picture. The picture is "repeated" at the same rate as the antenna rotates, approximately 13 revolutions per minute, or once every 5 seconds. Each time the radar picks up an object such as another vessel, a buoy, or shore lines, a bright glow or spot shows on the scope. The position of these objects (echoes) from the center (your ship) is used to determine bearing and range. The scope should be viewed in subdued light, using the light hood to exclude outside light in the daytime. The picture is brightest at the instant the antenna is pointing at any object. The picture then gradually fades until the next revolution of the antenna picks up the object again. This shows the relative movement between your ship at the center and the echoes as they assume new positions on the scope. k-G TYPICAL VIEW OF NARROWS NEW YORK HARBOR AS SEEN ON RADAR SCOPE Courtesy of Sperry Marine Systems Division h-1 BEARING CURSOR The cursor knob, lower right corner near scope, rotates a series of parallel lines over the scope. The crossed center lines show the hearing compared with the azimuth scales. The other lines are useful for estimating passing distance and in plotting. FIXED AND STABILIZED AZIM UT H SCALE Two 360 degree scales at the periphery of the scope are each calibrated in divisions of one degree. One scale is fixed. When the indicator is fitted with a "stabilized azimuth scale", the other scale is automatically rotated by a repeater motor connected to the ship'.s gyro compass. If the indicator does not include the "stabilized azimuth scale", this scale may be rotated manually to coincide with your own ship' s course. The knob for this scale is in the lower left corner near scope. This knob is pulled up to engage gears for scale setting or rotation. When pushed down, the knob is disengaged. In the "down", accidental pressure on the knob will not interfere with rotation when the scale is driven by the repeater motor. NORTH STABILIZED P IC TURE Some indicator units are fitted with an accessory that stabilizes the picture instead of stabilizing the rotating azimuth scale. When stabilized picture, north is always "UP", that is, at zero on the fixed scale. The picture remains "stationary" when your own ship changes course. The picture can of course be switched to relative display if it is desired to have ship's heading "UP". h-Q RELATIVE DISPLAY AMD TRUE DISPLAY Depending upon the type of display selected, bearings taken with the cursor may be True Bearing, or Relative Bearing. When Relative Bearing is selected, the heading flash is always at zero on the fixed scale, regardless of the heading of the ship. When True Bearing display (North Stabilized) is selected, the heading flash points to your own ship' s course on the fixed scale. For example, the heading flash will occur at k-5 degrees when your own ship is proceeding Northeast. When the indicator is fitted with the "North Stabilized" accessory, the operator may select True or Relative Bearing display with the switch at upper left corner of the indicator. An indicating light shows the type of display selected. When the indicator is fitted with a stabilized azimuth scale, the picture itself is always relative. When your own ship changes COURSE, THE PICTURE rotates and the ship' s heading is at the top of the scope. These same conditions exist if the azimuth scale is not stabilized and is manually set to ship' s course. The following simple rules show the use of the fixed and movable scales under any condition: 1. North Stabilized Picture at "True" (on). Read True Bearings against movable scale, provided the latter has been manually set to ship' s course. 2. North Stabilized Picture at "Relative" (off). Read True Bearings against movable scale provided latter has been manually set to ship' s k-9 course. Line up course on scale with heading flash to do this. Heading flash always points to zero on fixed scale. 3- North Stabilized Azimuth Scale. Read true hearings against movable scale. Read relative hearings against fixed scale. k. With no stabilized picture or scale. Read true or relative bearings as in (2) above since conditions are the same (relative display). SIB/MARY OF BEARING SCALE FUNCTIONS Relative bearing display: Ship's heading "Up" on scope. Fixed scale - relative bearings and movable scale - true bearings. True bearing display: North "Up" on scope. Fixed scale - true bearings and movable scale - relative bearings. RANGE LIGHTS AND RA NGE SCALES The operator may select any one of six ranges to suit conditions for the area to be viewed. Range scales are 1/2, 1, 2, 6, 16 and Ko miles. Ranges are calibrated in nautical miles (6080 feet) or statute miles (5280 feet) as specified by the customer. A row of six lights above the scope shows the range in use. The range switch is one of the four large knobs on the horizontal control panel near the main nameplate on the indicator unit. F IXED RANGE RINGS There are four fixed rings for each range scale. The intensity of the range rings is regulated by the control marked "Fixed Ring Int." The variable rings may be left on, if desired, or turned off with its U-10 0, •125 0, • 25 0. ■ 5 1, • 5 k, ,0 10, .0 control. Spacings between the fixed rings are as follows. RANGE SWITCH SPACING IN MILES 1/2 1 2 6 16 ko VARIABLE RANGE MARKER (VRM) The variable range marker is an adjustable range ring circuit that covers l/2 to 30 miles in steps of one-tenth mile. A mechanical counter is mounted at the right of the range indicator lights. The knob for this counter is at the extreme upper right corner of the indicator. The counter has three digits with the last (third) digit reading tenths of a mile. Operation of the variable marker is described below. 1. Tarn the counter knob until the reading is somewhere near the range scale in use. 2. Adjust the control marked "Variable Ring Int." until the ring on the scope is sharp and clear, but not too bright. Turn out, or dim the fixed range rings, if desired, with control marked "Fixed Ring Int." 3- Adjust counter knob until the ring just touches the object whose range is to be measured. Read distance on counter. 4-11 k. Typical ranges and counter readings, RANGE COUNTER RANGE SWITCH READING IN MILES 1/2 _ _ 1 005 (min) 0.5 1 010 1.0 2 Oil 1.1 2 018 1.8 6 022 2.2 6 058 5-8 16 112 11.2 16 158 15-8 40 202 20.2 4o 300 (max) 30.0 INDICATOR - MAIN CONTROLS (LEFT TO RIGHT) Power Switch: Off - Standby - Operate When the power switch is turned from OFF to either the STANDBY or OPERATE positions, a time delay of approximately 3 minutes occurs before the picture becomes visible. This allows warm up of the vacuum tubes. STAND- BY is used to keep the tubes warm with power removed from the transmitter circuits. The operator may, if desired, switch directly from OFF to OPERATE, and after 3 minutes view the picture. ANTI-CLUTTER CONTROL This limits the degree of sea return, or "clutter", and should be used with caution while the picture is being observed. Too high a setting may cause objects to be "lost" in sea return, even though the area near your ship appears to be "clear". It is better practice to adjust for slight amount of sea return while observing objects. 4-12 RANGE SWITCH This is a 6 position switch for selecting the desired range; namely, l/2, 1, 2, 6, 16 and kO miles. GAIN CONTROL This control regulates the sensitivity (gain) of the radar receiver. Observe the scope and use only enough gain to make objects stand out clearly. Too high a setting causes blurring and loss of definition. Too low a setting will reduce pickup at the outer areas of the scope. INDICATOR SECONDARY CONTROLS The Secondary Controls are located directly below the four Main Controls. These are called "Secondary Controls" because they are adjusted only occasionally, or under special conditions described below. CONTRAST Used to regulate brightness of picture. Avoid too high a setting that may make picture fuzzy. Adjust for clear, sharp display. FLASHER Used to regulate intensity of heading flash. A fairly dim heading flash is generally preferred so as not to obscure echoes directly under the flasher. An aft flash is also provided. This is useful in rivers or channels to show a "line" astern. When using a North Stabilized picture, only the heading flash is present. This indicates the ship' s course on the fixed scale. ^-13 DIMMER This control regulates the light intensity of the azimuth scales and the plastic control panels. Adjust to suit conditions. ECHO BOX The Echo Box toggle switch is usely only when the radar is fitted with an echo box for checking and testing purposes. When the switch is ON, "Spokes" (artificial echoes) are seen in the scope, extending out to about 1 3,A mile. Spokes shorter than usual indicate that the radar requires service work to restore ranges to their normal performance. FTC SWITCH FTC means "fast time constant." It is a receiver circuit that reduces the apparent depth of objects. During sea return, heavy rain, or snow, or when observing land masses, placing the FTC switch in the ON position helps to clarify the picture. V ARIABLE RING I NT. This control regulates the intensity of the variable range ring. FIXED RING INT . This control regulates the intensity of the four fixed range rings provided for each range scale. The fixed and variable rings may be used together, or either may be used separately. ^-14 FOCUS The picture is focused by adjusting this control. To obtain proper focus, observe the picture and adjust the FOCUS control for clear, sharp echoes. GYRO RESET A "Gyro Reset" switch is located behind the hinged panel below the secon- dary controls. This switch is for the convenience of the observer. In the OFF position, the switch temporarily disconnects the circuits between the ship' s gyro compass, and in the indicator, the repeater motor used for "NORTH UP" stabilization, or azimuth scale stabilization. This can be accomplished without operating the radar. In principle, the function is the same as resetting any bearing repeater after shut-down and start-up of the master gyro compass. The Gyro Reset switch removes power from the indicator circuits during reset, preventing internal gear damage from manual resetting. The drum-type scale, calibrated in degrees, is used only on indicators fitted with the North Stabilized accessory. The scale is rotated, by finger pressure, to the ship' s course which is indicated by the gyro compass For indicators having the Stabilized Azimuth Scale, pull up on the scale knob to engage the gear, then set the scale to the ship' s course against zero on the fixed scale. Push the knob down to disengage the gear. NOTE: In all cases, immediately after reset, place the GYRO RESET switch 4-15 in the ON position, and double check to make sure that the scale shows the correct course and follows the normal "hunting" of the gyro system. OTHER CONTROLS The test meter, meter switch, antenna switch and the rows of locked calibration controls adjacent to the Gyro Reset switch are for the service technician and are covered in appropriate sections of the R.M.C.A. Eadar Manuals. Do not tamper with the calibration controls. k-l6 INDICATOR OPERATING PROCEDURE The controls are normally operated in the following sequence: POWER SWITCH : Place in OPERATE position. Radar will be operative after 3 minutes. Use STANDBY position if radar is to be kept warmed up before or after actual operation. RANGE : Select desired range l/2, 1, 2, 6, l6 or kO miles. ANTI- CLUTTER : Set at zero for initial setting. GAIN : Adjust for clear , sharp picture. If sea return is appreciable, slowly advance ANTI-CLUTTER control but avoid too high a setting as this may cut out nearby objects. DISPLAY : Select TRUE or RELATIVE bearing display. NOTE : This applies only to radars fitted with the North Stabilized accessory unit. CONTRAST : Adjust for clearest picture. FLASHER : Adjust for desired brightness of heading flash. DIMMER : Adjust for desired azimuth scale illumination. FTC: Normally OFF. Turn ON to reduce clutter. VARIABLE RING INT. : Adjust brightness of variable range rings. FIXED RING INT. : Adjust brightness of fixed range rings. FOCUS : Adjust for clearest picture. NOTE : GAIN and ANTI-CLUTTER controls are important adjustments in re- lation to the range scale in use. Do not assume that the highest settings give the "best results. Observe the scope, and adjust these controls for the clearest picture. Nearby objects require a low GAIN setting, while objects further away will usually be observed better with higher settings. 4-18 Courtesy of Sperry Marine Systems Division SPERRY MK SCALE TRUE BEARING ON-OFF SWITCH INSTALLED WITH TRUE BEARING ALONE RANGE VIDEO HEADING LIGHT DIMMER OFF-STANDBY- ON SWITCH RADAR INDICATOR CONTROLS Courtesy of Sperry Marine Systems Division 4-20 MARINERS PATHFINDER ILLUMINATED NUMERAL INDICATES RANGE (1,2, 4,8,20 OR 40 MILES) IN USE. ILLUMINATED LETTERS "RB" INDICATE RADAR SET FOR RAYMARK BEACON RECEPTION ON RADARS HAVING RAYMARK BEACON KITS. DIMMER ADJUSTS BRIGHTNESS OF DIAL LIGHT ILLUMINATION CURSOR ADJUSTS POSITION OF BEARING CURSOR STC-GAIN ADJUSTS SENSITIVITY OVER RANGE OF TO 8 MILES FLASHER ADJUSTS BRIGHTNESS OF SHIP'S HEADING FLASH AT ZERO RELATIVE FTC-ON WHEN "ON" (UP POSITION) LARGE MASSES ARE REDUCED TO SHOW OUTLINES AND PROMINENT OBJECTS. / KEYS UNLOCK FRONT AND COVER OF INDICATOR FOR SERVICING. SETS RANGE COVERED BY RADAR SCREEN. READY WHEN LIGHTED, INDICATES RADAR READY FOR OPERATION. COMPASS POSITIONS OUTER DIAL FOR TRUE BEARING READINGS. RING SET POSITIONS MOVABLE RANGE RING ON RADAR SCREEN FOR FOR RANGE MEASUREMENTS UP TO 20 MILES. MILES INDICATES POSITION OF MOVABLE RANGE RING. RING INT. ADJUSTS BRIGHTNESS OF MOVABLE RANGE RING. MARKERS ADJUSTS BRIGHTNESS OF FIXED RANGE RINGS. ROTATION CONTROLS ANTENNA ROTATION. UP- CLOCKWISE ROTATION. MIDDLE -ROTATION STOPPED. DOWN- COUNTERCLOCKWISE ROTATION. •1401 /A, 1402/A AND 1404/A - UP — CLOCKWISE ROTATION, MIDDLE — ROTATION STOP, DOWN — ROTATION STOP. MAIN OPERATING CONTROLS Courtesy of Raytheon Company 4-21 MARINERS PATHFINDER SYSTEM FUSE (7) PERFORMETER WHEN PRESSED, ARTIFICIAL SIGNALS ARE PRODUCED FOR CHECKING RADAR RAYMARK TUNE TUNES RADAR RECEIVER FOR RAYMARK BEACON RECEPTION ON RADARS WITH RAYMARK BEACON KITS INTENSITY ADJUSTS THRESHOLD OF RADAR SCREEN ILLUMINATION FOCUS ADJUSTS SHARPNESS OF RADAR SCREEN IMAGES JSE (7) TURNS RADAR "ON OR "OFF", OR PLACES RADAR IN STANDBY OPERATION SETS RANGE COVERED BY RADAR SCREEN INDICATES TOTAL OF OPERATING AND STANDBY TIME ADJUSTS OVERALL SENSITIVITY OF RADAR RECEIVER CHECKS VARIOUS CIRCUITS OF RADAR SYSTEM CENTER EXPAND WHEN "ON", ZERO RANGE AT CENTER OF SCREEN IS INCREASED TO AN AREA 1 INCH IN DIAMETER TEST METER SWITCH CONNECTS TEST METER TO C.iCUITS INDICATED AT SWITCH POSITIONS. FIGURES ARE RANGES OF NORMAL METER READINGS LOWER CONTROL PANEL CONTROLS Courtesy of Raytheon Company 4-22 CHAPTER k - PRINCIPES OF RADAR Section k.3 - MAINTENANCE AND SAFETY PRECAUTIONS SAFETY GUARDS AND WARNING SIGNALS When personnel are sent aloft in the area of rotating antennas, switches or motor controllers actuating the antenna movement shall be disabled and warning tags attached to prevent accidental energizing. Therefore, before starting any work on the antenna, remove the main line or antenna fuses and place a sign on the radar "DO NOT START - MEN WORKING ALOFT ON RADAR PLATFORM" . CAUTION Dangerous high voltages are present in both the indi- cator and transceiver. Even after the equipment has been off for some time a high voltage charge may be present. When covers are removed, safety precautions should be observed as follows: 1. Stop equipment. 2. Place the shaft of a long screw driver against the edge of the metal chassis. 3- Push the tip under each tube cap or the metal rim around the Cathode Ray Tube. SCANNER Paint periodically, using a thin coat of any paint that suits your color scheme. Care should be used not to paint the horn window. The wave guide, particularly the joints, should also be painted. All scanners have ^-23 gear cases containing oil, also drive motors and other bearings that require occasional oil and grease. Refer to instruction manuals. TRANSCEIVER If the scanner is mounted close to the stack, the horn plastic window should "be cleaned if soot forms. All transceivers contain blower motors which require periodic oiling. Air filters are also present which must "be replaced or cleaned. Refer to instruction manual s . INDICATOR - Dust will collect on the surface of the cathode ray tube and, therefore, it becomes necessary to clean periodically. CAUTION must be exercised in performing the cleaning operation. Due to the high vacuum and large surface area, a violent implosion may result if the face of the tube is struck. Exercise extreme care not to drop any heavy object on the tube face. MOTOR GENERATOR - Check brushes and lubricate bearings periodically. OVERALL MAINTENANCE - In order to prevent dampness from forming in equipment, operate set on full power for at least one hour each day at sea. Do not leave turned off for a PROLONGED PERIOD . k-2k k-25 < u to o LU > < 5 o mm c mm o mm -h : mm co : mm -h i *;*:*: > : mm -h : III to I :lil s i; Hi ^ |: lllll CO !; III a 1 111 co 'I « cor s o- CHAPTER 5 - INTERNATIONAL RULES OF THE ROAD - RADAR Section 5-1 - REVIEW OF RULES OF THE ROAD (As Applied To Radar) SPEED IN FOG RULE 16 (A) Every vessel, or seaplane when taxiing on the water, shall, in fog, mist, falling snow, heavy rainstorms or any other condition similarly restricting visibility go at a moderate speed, having careful regard to the existing circumstances and conditions. (b) A power-driven vessel hearing, apparently forward of her beam, the fog signal of a vessel the position of which is not ascertained, shall, so far as the circumstances of the case admit, stop her engines, and then navigate with caution until danger of collision is over. EARLY AND SUBSTANTIAL ACTION ALLOWED (C) A power-driven vessel which detects the presence of another vessel forward of her beam before hearing her fog signal or sighting her visually may take early and substantial action to avoid a close quarters situation but, if this cannot be avoided, she shall, so far as the circumstances of the case admit, stop her engines in proper time to avoid collision and then navigate with caution until danger of collision if over. PART D - STEERING AND SAILING RULES PRELIMINARY 1. In obeying and construing these rules, any action taken should 5-1 be positive, in ample time, and with due regard to the observance of good seamanship. 2. Risk of collision can when circumstances permit, be ascertained by carefully watching the compass bearing of an approaching vessel. If the bearing does not appreciably change, such risk should be deemed to exist. 3- Mariners should bear in mind that seaplanes in the act of landing or taking off, or operating under adverse weather conditions, may be unable to change their intended action at the last moment. k. Rules 17 to 2k apply only to vessels in sight of one another. POWER-DRIVEN VESSELS MEETING END ON RULE 18 (A) When two power-driven vessels are meeting end on, or nearly end on, so as to involve risk of collision, each shall alter her course to starboard, so that each may pass on the port side of the other. This rule only applies to cases where vessels are meeting end on, or nearly end on, in such a manner as to involve risk of collision, and does not apply to two vessels which must, if both keep on their respective course, pass clear of each other. The only cases to which it does apply are when each of two vessels is end on, or nearly end on, to the other; in other words, to cases in which, by day, each vessel sees the masts of the other in a line, or nearly in a line, with her own; and by night, to cases in which each vessel is in such a position as to see both the sidelights of the other. It does not apply, by day, to cases in which a vessel sees another ahead crossing her own course; or, by night, to cases where the red light of one vessel is opposed to the red light of the other or where the green 5-2 light of one vessel is opposed to the green light of the other or where a red light without a green light or a green light without a red light is seen ahead, or where both green and red lights are seen anywhere hut ahead. (B) For the purposes of this Rule and Rules 19 to 29 inclusive, except Rule 20 (c) and Rule 28, a seaplane on the water shall be deemed to be a vessel, and the expression "power-driven vessel" shall be construed accordingly. TWO POWER-DRIVEN VESSELS CROSSING RULE 19 When two power-driven vessels are crossing, so as to involve risk of collision, the vessel which has the other on her own starboard side shall keep out of the way of the other. PRIVILEGED VESSEL DUTY RULE 21 Whereby any of these Rules one of two vessels is to keep out of the way, the other shall keep her course and speed. When, from any cause, the latter vessel finds herself so close that collision cannot be avoided by the action of the giving-way vessel alone, she also shall take such action as will best aid to avert collision (see Rules 27 and 29). BURDENED VESSEL DUTY RULE 22 Every vessel which is directed by these Rules to keep out of the way of another vessel shall, so far as possible take positive early action to comply with this obligation and shall, if the circumstances 5-3 of the case admit, avoid crossing ahead of the other. RULE 23 Every power-driven vessel which is directed hy these Rules to keep out of the way of another vessel shall, on approaching her, if necessary, slacken her speed or stop or reverse. OVERTAKING VESSEL RULE 2k (A) Notwithstanding anything contained in these Rules, every vessel overtaking any other shall keep out of the way of the overtaken vessel. (B) Every vessel coming up with another vessel from any direction more than 22 l/2 degrees (2 points) abaft her "beam, i.e., in such a position, with reference to the vessel which she is overtaking, that at night she would be unable to see either of that vessel's sidelights, shall be deemed to be an overtaking vessel; and no subsequent alteration of the bearing between the two vessels shall make the overtaking vessel a crossing vessel within the meaning of these Rules, or relieve her of the duty of keeping clear of the overtaken vessel until she is finally past and clear. (C) If the overtaking vessel cannot determine with certainty whether she is forward of or abaft this direction from the other vessel, she shall assume that she is an overtaking vessel and keep out of the way. GENERAL PRUDENTIAL RULE RULE 27 In obeying and construing these Rules, due regard shall be had to all dangers of navigation and collision, and to any special cir- cumstances, including the limitations of the craft involved, which may render a departure from the above Rules necessary in order to avoid 5-h immediate danger. RULE 28 (A) When vessels are in sight of one another, a power-driven vessel under way, in taking any course authorized or required by these Rules, shall indicate that course by the following signals on her whistle; namely: One short blast to mean "I am altering my course to starboard". Two short blasts to mean "I am altering my course to port". Three short blasts to mean "My engines are going astern" . DANGER SIGNAL (B) Whenever a power-driven vessel which, under these Rules, is to keep her course and speed, is in sight of another vessel and is in doubt whether sufficient action is being taken by the other vessel to avert collision, she may indicate such doubt by giving at least five short and rapid blasts on the whistle. The giving of such a signal shall not relieve a vessel of her obligations under Rules 27 and 29 or any other Rule, or of her duty to indicate any action taken under these Rules by giving the appropriate sound signals laid down in this Rule. WHISTLE LIGHT (C) Any whistle signal mentioned in this Rule may be further indicated by a visual signal consisting of a white light visible all round the horizon at a distance of at least 5 miles, and so devised that it will operate simultaneously and in conjunction with the whistle sounding mechanism and remain lighted and visible during the same period as the sound signal. 5-5 SPECIAL RULES (D) Nothing in these Rules shall interfere with the operation of any special rules made "by the Government of any nation with respect to the use of additional whistle signals between ships of war or vessels sailing under convoy. RULE OF GOOD SEAMANSHIP RULE 29 Nothing in these Rules shall exonerate any vessel, or the owner, master or crew thereof, from the consequences of any neglect to carry lights or signals, or of any neglect to keep a proper lookout, or of the neglect of any precaution which may be required by the ordinary practice of seamen, or by the special circumstances of the case. 5-6 CHAPTER 5 - INTERNATIONAL RULES OF THE ROAD - RADAR Section 5.2 - ANNEX TO THE RULES RECOMMENDATIONS ON THE USE OF RADAR INFOR- MATION AS AN AID TO AVOIDING COLLISIONS AT SEA (1) Assumptions made on scanty information may be dangerous and should be avoided. (2) A vessel navigating with the aid of radar in restricted visibility must, in compliance with Rule 16 (A), go at a moderate speed. In- formation obtained from the use of radar is one of the circumstances to be taken into account when determining moderate speed. In this regard, it must be recognized that small vessels, small icebergs and similar floating objects may not be detected by radar. Radar indications of one or more vessels in the vicinity may mean that "moderate speed" should be slower than a mariner without radar might consider moderate under the circumstances. (3) When navigating in restricted visibility, the radar range and bearing alone do not constitute ascertainment of the position of the other vessel under Rule l6 (b) sufficiently to relieve a vessel of the duty to stop her engines and navigate with caution when a fog signal is heard forward of the beam. (4) When action has been taken under Rule l6 (C) to avoid a close quarters situation, it is essential to make sure that such action is having the desired effect. Alterations of course or speed or both are matters as to which the mariner must be guided by the circumstances of the case. 5-7 (5) Alteration of course alone may "be the most effective action to avoid close quarters provided that: (A) There is sufficient sea room. (B) It is made in good time. (C) It is substantial. A succession of small alterations of course should be avoided. (D) It does not result in a close quarters situation with other vessels. (6) The direction of an alteration of course is a matter in which the mariner must he guided by the circumstances of the case. An alteration to starboard, particularly when vessels are approaching apparently on opposite or nearly opposite courses, is generally preferahle to an alteration to port. (7) An alteration of speed, either alone or in conjunction with an al- teration of course, should be substantial. A number of small alterations of speed should be avoided. (8) If a close quarters situation is imminent, the most prudent action may be to take all way off the vessel. 5-1 CHAPTER 5 - INTERNATIONAL RULES OF THE ROAD - RADAR Section 5-3 - AVOIDING COLLISION IN RESTRICTED VISIBILITY Avoiding collision in restricted visibility can be achieved by early recognition of the existence of danger. When the possibility of collision exists and the circumstances of the case understood, then proper evasive action should be taken in suf- ficient time to ensure that the collision will be avoided. Under the present Rules of the Road and court opinions, mariners have a duty to use properly the information obtained from radar in re- stricted visibility. The mariner's responsibility is complicated by the fact that the steering and sailing rules (Rule 17 through 2k) do not apply unless he has visual contact with the other ship. The situation when using radar in re- stricted visibility is similar to the situation where two fishing vessels are approaching each other so as to involve risk of collision. There is no privileged or burdened vessel, and both must act under the good seamanship rule (Rule 29)- Other pertinent rules that are op- erative when visual sighting has not been made are: 1. Rule 27 - If there is an immediate risk of collision. 2. Rule l6 - If fog signal, is heard forward of the beam. 3- Rule l6 - For moderate speed. k. Rule 29 - For sounding proper signals and lookouts. When using true or relative motion radar to predict whether or not another ship is approaching so that the possibility of a collision 5-9 exists (close quarters situation), the mariner must use some form of plotting or a computer that will solve the problem for him. It is the mariner's responsibility to determine what constitutes a close quarters situation for his vessel. As a recommendation, it is sug- gested that it can be computed by using the relative speed and the time required for own ship to make a crash stop. For example, if own ship requires 6 minutes to make a crash stop and the other ship is approaching forward of the beam with a relative speed of 30 knots, then the minimum distance the other ship could be allowed to close would be 3 miles. In the above example, if the relative plot indicated that the other ship was approaching so as to pass less than 3 miles, then there is danger, and the possibility of a collision exists. If the range closes to 3 miles or if a fog signal is heard forward of the beam (indicating the existence of danger) then a crash stop should be made. When the possibility of collision exists and the range of the other ship is such that Rule 27 is not invoked (no immediate risk of col- lision), it is the mariner's responsibility to determine whether evasive action is to be taken through maneuvering own ship by changes in course and/or speed to employ the crash stop method. Whatever his decision, action must be taken early and it must be bold. This has two purposes, just as it has in good visibility. First, bold action clearly indicates the intentions of own ship to the other ship so she can perform her duty in assisting in avoiding 5-10 close quarters. Second, action taken early makes the action more effective. The direction of a course change and the amount of a speed change are matters that the mariner must determine from the circumstances, including whether or not own ship' s action will cause a close quarters situation with other vessels in the vicinity. As previously discussed, there is no privileged or burdened vessel when visual sighting has not been made. This does not mean that it is every man for himself and the devil take the hindmost. The action taken must be the action required by the good practice of seamen under Rule 29 - in other words, the action required by the particular situation. In this regard, it must be borne in mind that own ship is only concerned with other ships forward of the beam. Ships abaft the beam should stop when hearing own ship' s fog signal, thereby minimizing any danger. It is suggested that course changes to the left would not be considered prudent except when own ship is overtaking another ship and changes course to the left to avoid crossing ahead when passing. Due to the fact that most ships respond faster to changes in course than changes in speed, course changes are considered more effective than speed changes in avoiding close quarters situations. To sum up, action taken should be taken early and it should be substantial to make own ship' s intentions im- mediately apparent to the other ship and the circumstances of the case must be considered when taking evasive action. When evasive action has been taken, mariners have the additional duty of ensuring that the action is having the desired effect. If the action is not having the desired effect and the existence of danger is still 5-11 present, then the crash stop method should be used if there is no other prudent alternative, in sufficient time to ensure that collision will he avoided. If the action taken to avoid close quarters is having the desired effects, the mariner must then determine when it will be safe to resume his original course and/ or speed. The human element factors are very much involved and add to the diffi- culty in determining the solutions of the collision prevention problem. They largely depend on the mariner's confidence in his radar, his radar plotting skill, his skill in adjusting and interpreting the radar and his knowledge of the particular handling characteristics of his ship and the Rules of the Road. As the reader might assume, the use of radar is limited to keeping ships out of close quarters situations. A ship involved in a close quarters situation and having made a crash stop is best maneuvered clear by the use of the fog signals on the whistle. For example, suppose after making a crash stop your ship and the other ship are both using two pro- longed blasts. One vessel should initiate the action to maneuver clear by sounding one prolonged blast (indicating that she has way on). The other ship should remain stopped and indicate that action by continuing to sound two prolonged blasts in answer to the other ship' s one prolonged blast whistle signals until there is no longer any danger and then both vessels can proceed. 5-12 CHAPTER 6 - FUNDAMENTALS OF RADAR PLOTTING Section 6.1 - MANEUVERING BOARD H.O. 2665, SERIES The MANEUVERING BOARD 2665 Series, which represents a polar diagram, consists of ten concentric circles, equally spaced, representing dis- tance in miles. It is graduated in azimuth throughout 360 . It was designed with a view toward locating other vessels with respect to own ship which is located in the center of the board. This center may he considered The Eye, such as the eye of a hurricane, but in this case we consider it the eye of the radar, which we always identify as Since the eye of a hurricane cannot move out of its center, neither can the eye of the radar move out of the center of the maneuvering board. Examine a radar unit in operation on relative motion presentation. In the dead center of the scope, we see a small blob of light - The Eye. The eye does not move from this position at any time, but keeps search- ing round and round in azimuth, finding ships, land, buoys and other objects which are of concern to the radar observer. If we wish to transfer what we see on the radar scope to a piece of paper, which we call the maneuvering board, we must do so maintaining each and every detail of what we see. First, we must locate the eye in the center which we know is "own ship" since the radar is part of our ship. 6-1 The azimuth circle and cursor on the radar assist us in finding the true direction of pips or contacts that appear on the radar scope. A range circle or variable marker assists us in determining the exact range or distance the pip or contact is from our "own ship". Having thus plotted the contact on the maneuvering hoard, we have a permanent record of where it was with relation to "own ship" for a given time. Let us wait now for 6 minutes and at least plot it every 3 minutes. We repeat the above, obtaining a second range and bearing. Again we plot this information on our maneuvering board. What has happened? Our radar has told us that the pip has moved. By drawing a straight line from the first position (Ml) through the second position (M2) of the target, and extending this line toward the center of the maneuvering board, we establish what is known as a Relative Movement Line (RML). This line will tell us how close this pip or contact will come to our "own ship". We call this CPA, or closest point of approach. But let's back up for a moment. Why did we call this the Relative Movement Line? Is this not the contact's true course? Unfortunately, many radar observers think so and, ap- parently, this is a contributing factor in the many cases of collision we read about almost daily. If you think about it one moment, our ship is making way through the water perhaps at 15 or 20 knots, yet we maintained a position in the center or eye of our radar and plotted it as such on the maneuvering board. If 6-2 we have motion then where is it? On a relative motion radar, all of our motion is added to that of the other fellow, i.e., our course, our speed. Take, for example, two automobiles travelling toward each other on the highway. You are in one car doing 50 MPH. The other fellow is also doing 50 MPH. How fast are you approaching each other? Certainly, 100 MPH. This is called relative speed. Part of it is yours and part of it is his. It would take a very unusual person merely watching a moving contact on a radar to determine its true course and speed without going through the mechanics of plotting. Perhaps the Martians can do it; we know we can't. But until such time as we can employ a few Martians to second guess standard plotting techniques, let's get on with it... some- body has to. There are three radar navigational problems which may be solved. First, to determine the Closest Point of Approach or CPA. Second, to determine the approaching vessel's true course and speed. Third, to determine the new course, speed, or both, to follow to avoid a close quarters situation and clear the other vessel by a given distance. These problems can be solved quickly and accurately through the use of a relative motion plot. A true m6tion plot, which is accomplished by advancing "own ship" along the course line, is not recommended. Such a plot is very time consuming and requires tedious calculations to determine how far each will pass 6-3 or if crossing is ahead or astern. It is also not practical for cal- culating corrective course measures. However , there is a method by which true motion is combined with relative motion and is considered as an alternate method of plotting. This method is described in Chapter 7, Section 7«6, entitled True Motion. A relative plot in contrast to the true motion plot shows relative motion. In making a relative plot, all bearings and ranges are plotted from "own ship' s" position maintained at the center of the board. An extension of the RML, Ml - M2, past the center of the board in the direction of the motion will provide the passing distance and position of the target ship and "own ship". This line immediately shows whether there is any possibility of a collision and how close the passing will be. To determine the target ship' s course and speed, a resolution of a vector triangle is next in order. The relative course and speed and "own ship's" course and speed form two sides of the triangle. The resolution of the third side will provide the target ship' s course and speed. If it should become necessary to change course, the new course can be determined by selecting a new RML and plotting this with the contact ship's course and speed will form two sides of a triangle. The resolution of the third side will give the new course or speed as desired. The further ap- plication of this technique, together with all of its subtleties, will be discussed at length in class. G-k CHAPTER 6 - FUNDAMENTALS OF RADAR PLOTTING Section 6.2 - LOGARITHMIC TIME, SPEED AND DISTANCE SCALE cq bO 0) M d) d 0) J -p d •H a> CQ <+H t> O •H O -H S3 d o3 -P bO -P cd CU CU CO H 43 -H ■P Q p ' — ' • CU O CQ d H H CD d cu 0) CU cti d ft O CU -H cq o3 !h !> H ft -H CQ Ph CQ d •H 43 l CU Cm P> 43 o -— > -P P m bO aj 2 bO cu O S3 H co M -H cu bO P p 0) s=l ch pi a o3 cu . S3 O 43 H cq •H — O CU s O -P S3 -H VO vo 2 3 a O K u S3 43 CVJ o O -P CQ CH •H CU CQ d bO 3 03 cu S3 43 U ^S-H ■P CU d--^43 . . H CU £ •H CU VO a Eh ft S3 3 • — 'CQ S3 3 K co -p CQ O P> tfl C\J •H CU CQ •H -d"-^ -H Q CQ bO -H d •H e-« (p cu Eh d d O h-3^-^ cu C d CU 43 :H CU H bO d bO -P £ CU (D CU cu ft > H cu H cu o CQ 03 ft P Eh H -P CQ -P cd CQ -p 43^43 V _ • • bO bO -H . • H CU [25 •H CQ -H d S 0) O O H JH M S3 H CQ 3 H CU -H J CQ a3 F-i cu d cu m (D P l^ o -h a r-i o !> CQ J o5 > cd H K •H O H -H ,-\ -H Ph H 1 EH C3 W I CQ N Ph i H h-H CO 1 Q P3 o M 1 R rl m 1 CQ W Ph 1 H i-l CQ 1 P3 O Q 09 09 Ot? oe 92 02 91 t> 6-5 CD CO ^j U 03 CD P £l -P t3 Oh o •H CD -H -P >Hfl •H •H J3 T3 CD Til O -V rH Ch cd CD Pi O H S O ft -H 13 bO P CD co iaD H ^ Ch Pi O o -P t3 H ch -h co CD > CD > H -H P O T3 PS M CD Pi O CD -H 03 ^1 a • H -P Pi •H 1)4 o VQ > CD ■r! H •H ft Pi -P t3 CO O cd co •• — -* Pi •H o- CH ^~n •H CO O VQ bO a T3 CD H CD u 0) H bO J CD OJ •H CD Pj -p ft a H O CD CO o ^ -H a Ph CQ 03 H t3 O J CO M g CD CD ^-^ LfA m CD -p O CD H o > P cd ft bO w O 8 rH CO CD CO PL, H ht leg (Time Leg) on 6. withou (Time Leg) on 60, left leg wil (>• bO d co q p 1 05 XI CD bO A PO -H -P H CO CD •H d xi o -P -P aJ .— s CD Leg plac • CD CO O CO CD q u -p ccj CD • 3 -P tj CO s co -h p •H ■H i> O a q -h a VD CO CD CO £ 5h X! H • • •H CD p t3 t3 m CD co •H tH -H CD CD f> o & H •H X! CO •H -d t? o a 03 -H t3 <+H CD ,3 fl oo O fH [S •H • ft fo H UO ra t3 CD CD o £ H CD CD EH cc5 X ft !h p> p> CO • • <+H • • H s CD bD CD s o H id -p |jq CQ H •H 03 J CQ B CD bu O pq CD O Pi -H o > i-i otS a3 t3 P>4 < 8 Pn o -h 09 09 oe OS 91 i Eh O M i CO m a. i H ^ CO o Q 6-7 CHAPTER 6 - FUNDAMENTALS OF RADAR PLOTTING Section 6.3 - TIME, SPEED AND DISTANCE PROBLEMS TO FIND SPEED - Place right point of dividers on elapsed time and left point on distance. Without changing the spread of the dividers, place the right point on 60; left point will then indicate speed. TO FIND DIS- TANCE OR TIME Place right point of dividers on 60 and left point on speed. Without changing the spread of the dividers, place the right point on time; left point will then indicate distance. Or, place left point on distance, right point will then indicate time. 7 8 9 10 n 12 13 Ik 15 16 IT 18 TIME, RELATIVE SPEED AND DISTANCE PROBLEMS PROBLEM DISTANCE TIME 6 . 2 . 10 12 50 6 SPEED 1 . . . • 3 2.5 2.7 Ik 2 . DISTANCE 1 . . . 1.6 10 9 . 12 6 . TIME 10 45 6 . 30 17 20 SPEED 8 . 20 26 21 Ik 17 SPEED 15 • Ik . 19 • 18 . 13-5 10 . Kts. "Kts. "Kts. "Kts. "Kts. "Kts. TIME _Mins, Mins. Mins, Mins. ~Mins. Mins. DISTANCE Mi, Mi. "Mi. "Mi. "Mi. 6-8 ANSWERS TIME, SPEED AND DISTANCE PROBLEMS PROBLEM SPEED PROBLEM TIME PROBLEM DISTANCE 1 2 10 9 7 8 7-5 k.8 13 Ik 2.5 10.5 3 k 5 6 15 13.5 16.8 20 9 10 11 12 23 26 51 21 15 16 17 18 1-9 9 3.8 3-3 6-9 CHAPTER 6 - FUNDAMENTALS OF RADAR PLOTTING Section G.k - MANEUVERING BOARD SYMBOLS PLOTTING SYMBOLS FOR PLOTTING CONTACTS SYMBOL MEANING R Own ship . M Other ship. Ml First observed position of other ship. M2, M3 Later positions of other ship. The designations Ml M2, Ml M3> etc. indicate the RML along which M appears to move; always in same direction as rm. RML Relative Movement Line. Mx Position of other ship on RML at planned evasive action (point of execution). RML 1 New Relative Movement Line. CPA Closest Point of Approach FOR PLOTTING (COURSE- SPEED) VECTORS e The origin for any ship's true (course- speed) vector. r The end of own ship's true (course- speed) vector, er; also the origin of the relative (course- speed) vector, rm, which is always in same direction as Ml M2. rl r2 The ends of alternative (course- speed) vectors for own ship. m The ends of other ship's true (course- speed) vector, em; also the end of the relative (course- speed) vector, rm. ml m2 The ends of alternative true (course- speed) vectors for other ship and alternative relative (course- speed) vectors. DRM Direction of Relative Movement; always plotted in the direction of rm. SRM Speed of Relative Movement; relative speed. MRM Miles of Relative Movement; relative distance traveled. 6-10 CHAPTER 6 - FUNDAMENTALS OF RADAR PLOTTING Section 6.5 - THE RELATIVE MOTION PLOT DETERMINATION OF CLOSEST POINT OF APPROACH (CPA) (1) Draw a vector from the center (e) of the maneuvering board in the direction of your own ship's course and with a length equal to your own ship's speed (er). (2) Plot initial range and bearing of contact (Ml) and record time. NOTE: Plotting intervals should be sufficient to obtain enough positions to make an accurate determination of the contact's relative movement. (3) At a predetermined interval of time, plot second and third range and bearing of same contact and label as M2 and M3 and record time. (k) Draw Relative Movement Line (RML) by connecting Ml with latest M and extend line past the center of the maneuvering board. (5) Draw a line from the center (e) of the maneuvering board perpendicular to the RML and label CPA. DETERMINATION OF TIME OF CLOSEST POINT OF APPROACH (CPA) (6) From the distance and elapsed time between Ml and latest M calculate relative speed using scales at bottom of the maneuvering board. Using relative speed, calculate time necessary for contact to move along RML from last bearing to CPA. 6-11 (7) Add this time to time of last bearing. This is the time of CPA„ THE FIRST VECTOR TRIANGLE DETERMINATION OF CONTACT'S TRUE COURSE (TC) AND TRUE SPEED (TS) (8) Using parallel rule, parallel RML to tip of own course and speed (r) and in the same direction of relative movement. (9) From the relative distance and elapsed time between Ml and latest M calculate the relative speed using scales at bottom of maneuvering board (1.5 miles in 6 minutes equals 15 knots). (10) Set the compass at 15 knots on the scale in use, place tip on (r), strike an arc on new RML and mark (m). (11) Draw true course and speed vector from (e) to the end of relative course speed vector at (m). The length of (em) represents the contact's true speed and where (em) is extended to cross the azimuth circle, represents the contact' s true course. THE SECOND VECTOR TRIANGLE DETERMINATION OF OWN SHIP' S NEW COURSE OR SPEED TO INCREASE CLOSEST POINT OF APPROACH (CPA) (12) At a determined point (Mx) on the RML, establish a point of execution that will require evasive action. Using relative speed and time between M2 and point of execution (Mx) determine the distance the contact ship will travel along the RML. (13) Draw a circle equal in radius to the new desired CPA. 6-12 (l^-) Draw the new Relative Movement Line (RML l) from point Mx tangent to the new desired CPA. NOTE : (Own Speed Circle) With a drawing compass placed at the center of cthe maneuvering board, swing an arc equal to own speed. If desired, it may be drawn through 36O . (15) Parallel new Relative Movement Line (RML l) with RML from point Mx and draw line in the opposite direction of indefinite length. (16) Own course and speed vector may intersect new relative course and speed line at two points. Either course change will yield the same CPA. However, one of the two possible course changes will direct own ship on a course parallel to other vessel, which may not be a desirable maneuver. (17) New crossing distance can be determined by length of new course line from center to point it intersects RML 1. DETERMINATION OF NEW CPA IF OWN SHIP CHANGES TO A SPECIFIED COURSE AND/OR SPEED (l8) A right angle from RML 1 to the center (e) is the new CPA. 6-13 H.O. 2665-10 SCALES 2:1 3:1 MANEUVERING BOARD 40 — 38 — 60 57— 36 — 54- 14 51 — 32 — 48 — 30 — 45 — 28 — 42 — 26 — 39 — 24 — 36 — 22 33 — 20 — 30 — 18 27- lb 24 — 14 21 — 12 — 18 — 10 — 15 — 8 — 12 — 6 — 9 — 4 — 6 — 2 3 - n — n-l SCALES 4:1 5:1 RELATIVE MOVEMENT Relative direction | Relative direction] Relative speed j r "* m Reference Ship R II Maneuvering Ship M True course and speed e «- rllTrue course and speed e 6-14 a s essi s TIME in minutes DISTANCE m yards Relative or actual 0ISTANCE in miles Given any two corresponding quai Per Pad of 50 H.O. 2665-10 SPEED in knots RETAPY OF THE f 5THED. JULY 1961 fj. O. 2665-10 H.O. 2665-10 MANEUVERING BOARD SCALES 4:1 5:1 >JC *-7o >9o *<# y 5^ u„ .,„«.,„ \y* logarithmic lime. ^X speed, and distance #> vX "*" s>^ ,.;;"f HsH : :;l:r'r:3 ■ if*\r . l ,;i;"i.«:;',i l ,TJ'"™"''" " """"""' > >^& .. i°,'.'™«°'i'" c .' °.".™; ..".':«""' el?,*.™ 5,0 o>-^ nico'irfll^^Heea^'talrX^rinwlMw'er^ lUJj- i - i>A \6° ^2,:;, ... „..„ t.r, be .„. ,„ ,N. ,.™ .„ „ ,„„... „n„ s Uce of 3 scale nomogram. Given any two corresponding quantities, solve lor third by laying rule through points on prop- I rice $1-(K> er sca | es ana - rea( j intersection on third scale. Per Pad of 50 H.O. 2665-10 6-15 TIME in minutes S S 3 SSSl ? !SSS S 8 DISTANCE in r 5THED.. JULY .961 H.O. 2665-10 H.O. 2665-10 SCALES 2:1 3:1 MANEUVERING tfOARD SCALES 4:1 5:1 40 — 38 — 60 ^7 36 54 — 34 51- 32 — 48- 30 — 45 — 28 — 42- 26 — 39- 24 — 36- 22^ 33 — 20 30 — 18 — 27 — 16- 24 — 14 — .'1 12 — 18 — 10 15 — 8 — 12 — 6 9 - 4 6 — 2 3 - — Suuoslod scales (or ololttng ol ranges ( measured in yard; From To Seal* yds. yds. 1,000 10.000 1:1 10.000 20.000 2:1 20,000 30,000 3:1 30.000 40.000 4:1 40,000 50,000 5:1 RELATIVE MOVEMENT Relotive direction Relative distance ( Relative direction | Relat,ve speed | Reference Ship R || Maneuvering Shi True course and speed e-*-r|| True course and speed e ■»- 6-16 TIME in minutes 3SSSS88 S § DISTANCE in yards , , Relative or aclual ?SS S 8 DISTANCE in miles Use ot 3 -scale nomogram. Given any two corresponding quantities, solve lor third by laying rule through points on prop l rice $1.00 er scales and read intersection on third scale. Per Pad of 50 H.O. 2665-10 "H ED.. JULY 1961 fj. O. 2665-10 CHAPTER 6 - FUNDAMENTALS OF RADAR PLOTTING Section 6.6 - MANEUVERING BOARD PROCEDURE - SPEED VECTOR DIAGRAM 1. Draw a vector from center of board representing our ship's course and speed. Draw a circle representing speed circle. Label center e (OWN SHIP), and extremity of line r distance for one hour. 2. Plot Ml and M2 of other (CONTACT) ship. Label Ml and M2 with time of bearings. 3- RELATIVE MOTION LINE is drawn thru these two points, past the center of the board. Mark RML on this line. k. RELATIVE SPEED is found by measuring distance between Ml and M2. Note TIME elapsed between Ml and M2. Using LOG SCALE, determine speed for one hour. I.E., distance run, 2 miles, time between Ml and M2 is 20 minutes. Set distance leg of dividers on 2 and time leg on 20. Without changing spread, shift dividers to 60 , and read 6 Knots . 5- Crossing Distance (CD) occurs at intersection of Line e - r and RML. Measure distance with dividers from center of board to this point. 6. CPA is a line drawn at RIGHT ANGLES to the RML, FROM the CENTER of the board; measure from center of board to THIS POINT , for RANGE , or DISTANCE of CPA and if extended to AZIMUTH CIRCLE gives the BEARING of CPA . 7- TIME of CPA is taken by measuring distance from M2 to CPA. Find on Log Scale how long it would take to travel this distance at RELATIVE SPEED. ADD this time to M2 and it will give time of CPA. 6-17 8. TARGET'S TRUE COURSE AND SPEED : Parallel RML up to r. Draw Line from r in direction of motion. Make length of line equal to ROTATIVE SPEED . Label extremity of line m; close triangle m to _e. DIRECTION of line em is target's TRUE COURSE , and length of line em equal target's TRUE SPEED . 9. NEW COURSE to steer, or NEW SPEED in order to avoid collision: A. Establish time of point of execution (Mx), and plot on RML Line. MARK (Mx), and Time. B. Draw new RML, (RML l) from point (Mx) tangent to desired new CPA. Label line RML 1. C. Parallel this line up to m and draw line intersecting SPEED C IRCLE at TWO POINTS . D. Where this line intersects speed circle will be New Course, rl. Label rl. Choice of two possibilities of rl depends on whether MINIMUM TIME required, or MINIMUM COURSE change required. E. CLOSE TRIANGLE from rl to e, and MARK COURSE in AZIMUTH Circle. 10. NEW SPEED is found at intersection of Lines m-rl and er. 11. NEW C. D. is found at intersections of RML 1 Line and rl Line. 12. NEW RELATIVE SPEED is found by measuring length of Line m-rl. 6-18 CHAPTER 6 - FUNDAMENTALS OF RADAR PLOTTING Section 6.7 - MANEUVERING BOARD PROBLEMS A navigator, while steering a course of at a speed of 5-5 knots, observes on his radar scope another vessel approaching forward of his starboard beam. At 10:00 a bearing and a range was taken from the radar screen and found to be 60° at 9 miles. At 10:20 the bearing was found to have changed to 59° at 7 miles. Since the bear- ing was not changing very rapidly it is evident that some action will be necessary. By use of relative plot, find Crossing Distance, Closest Point of Approach and time of Closest Point of Approach. Find True Course and Speed of contact. In plotting, radar pickup #1 will be called Ml, pickup #2, M2. ANSWERS CPA CD" RS t.cpa" TC" TS" NC~ NS~ NCD" The navigator wishes to keep all vessels at a distance of at least 2 miles. What course change should be made at 10": 30 for contact to clear ahead, in minimum time, with a Closest Point of Approach of 2 miles. Our course 0° Our speed 9 kts. TIME BEARING RANGE NOTE: In all problems, new speed is calculated on original course. ANSWERS Ml 11:00 80° 9 mi. M2 11:10 80° 8 mi. Find new course required for target to clear ahead, in minimum time, with a CPA of 3 miles. Time of course change 11:20. Closest point of approach Relative speed Time closest point of ap- proach True course True speed New course New speed New crossing distance . . . 6-19 Our course 270 Our speed 15 kts. TIME BEAMING RANGE Ml 3:00 210° 18 mi. M2 3:12 211° Ik mi. Find new course required for contact to clear ahead, in minimum time, with a CPA of 3 miles. Course change at 3:18. ANSWERS Closest point of approach Crossing distance Relative speed Time closest point of ap- proach True course True speed New course New speed New relative speed New crossing distance . . . Our course Our speed 10 kts. TIME BEARING RANGE Ml 4:00 10° 9 mi. M2 4:06 10° 8 mi. Find new course required for contact to clear ahead, in minimum time, with CPA of 1 mile. Course change at 4:12. ANSWERS Closest point of approach Relative speed Time closest point of ap- proach True course True speed New course New speed New crossing distance . . . New relative speed 6-20 Our course 150 Our speed ik kts. TIME BEARING RANGE Ml 12:00 55° ik mi. M2 12:20 56. 5° 10 ml. Find new minimum course change required for contact to clear ahead with CPA of 2 miles. Course change at 12:30. ANSWERS Closest point of approach Crossing distance Relative speed Time closest point of ap- proach True course True speed New course New speed New relative speed New crossing distance . . . Our course 70 Our speed 16 kts. TIME BEARING RANGE Ml 3:15 15° 18 mi, M2 3:27 16° 13 mi, Find new course required for contact to clear ahead, in minimum time, with CPA of 2 miles. Course change at 3:33- ANSWERS Closest point of approach Crossing distance Relative speed Time closest point of ap- proach True course True speed New course New speed New relative speed New crossing distance . . . 6-21 7. Our course 20 Our speed 7 kts. TIME BEARING RANGE Ml 7:00 90° 10 mi. M2 7:15 90° 8 ml, Problem A If the course was changed to 3^0° at 7:30, what would be the result. Problem B If the course was changed to 60° at 7:30, what would be the result. ANSWERS Closest point of approach Relative speed Time closest point of ap- proach True course True speed Problem A New closest point of ap- proach New relative speed Problem B New closest point of ap- proach New relative speed _ New speed New crossing distance . . . 8. Our course 160 Our speed 5 kts. TIME BEARING RANGE Ml 5:00 260° 10 mi. M2 5:10 260° 8.7 mi. Problem A If the course was changed to 180° at 5:20, what would be the result. Problem B If the course was changed to 220° at 5:20, what would be the result. ANSWERS Closest point of approach Relative speed _ Time closest point of ap- proach True course True speed Problem A New closest point of ap- proach New relative speed _ Problem B New closest point of ap- proach _ New relative speed _ New speed _ New crossing distance . . . 6-22 9. Our course 10° Our speed 9 lets. TIME BEARING RANGE Ml 9:55 89° M2 10:17 86 7-5 mi, k.9 mi, Speed change necessary, main- taining same course, for con- tact to clear ahead with CPA of 1.5 miles. Speed change at 10:29. ANSWERS Closest point of approach Relative speed True course True speed New speed 10. Our couse 3^0° Our speed 12 kts. TIME BEARING RANGE ANSWERS Ml M2 4:20 4:30 320 c 321 c 18 mi Ik mi, New minimum course change necessary for contact to clear astern with CPA of 2 miles. Time of course change 4:35- Closest point of approach Crossing distance Relative speed True course True speed New course 11. Our course 252° Our speed 16 kts • Ml M2 TIME : BEARING RANGE 3:08 3:28 195° 19^° 20 Ik. mi. ■ 5 mi Course change required for contact to clear astern with CPA of 2 miles. Course change at 3:^0. ANSWERS Closest point of approach Relative speed True course True speed New course 6-23 12/ Our course 113° Our speed 15 kts. TIME BEARING RANGE Ml 1:5^ 159° 6.5 mi. M2 2:00 158° k.3 mi. Find new course and new speed required for contact to clear ahead, in minimum time, with CPA of 1 mile. Course change at 2:03- ANSWERS Closest point of approach Relative speed True course True speed New course New speed 13, Our course 3^-2° Our speed 11 kts. TIME BEARING RANGE Ml M2 9:05 9:35 287° 288° 21 mi, 12 mi, New course required for contact to clear astern with CPA of 2 miles. We are increasing speed to 15 knots. Time of course change 9:^5. ANSWERS Closest point of approach Relative speed True course True speed New course at 15 kts. . . . Ik, Our course 80 Our speed 9 kts. Ml TIME BEARING RANGE 10:00 150° 9 mi. M2 10:18 152° 6 mi. Find minimum course change necessary for contact to clear astern with CPA of 1 mile. Course change at 10: 2k. ANSWERS Closest point of approach Relative speed True course True speed New course New speed 6-24 15- Our course 0° Our speed 9 kts. TIME BEARING RANGE Ml 10:00 60° 9 mi M2 10:20 59° 7 mi Find new course required for contact to clear ahead, in minimum time, with CPA of 2 miles. Course change at 10:30. ANSWERS Closest point of approach Crossing distance Relative speed Time closest point of ap- proach True course True speed _ New course New crossing distance . . . ANSWERS TO MANEUVERING ] BOARD PROBLEMS PROBLEM 3 PROBLEM 1 PROBLEM 2 CPA • 5 mi. CPA CPA 1.2 mi. CD . 6 mi. RS 6 kts. CD 1.4 mi. RS 6 kts% Time CPA 12:30 RS 20 kts Time CPA 11:30 TC 323° Time CPA 3:54 TC 297-5 TS 9-9 kts. TC 341° TS 6.1 New course 62° TS 19 kts New course 32.5° New speed 6.3 kts. New course 246° New speed 4 kts. New CD 4.4 mi. New speed 11.9 kts CD 2.8 mi. New RS New CD 25.5 kts 4 mi. PROBLEM 4 PROBLEM 5 PROBLEM 6 CPA CPA 1 mi. CPA 1 mi. RS 10 kts. CD 1.2 mi. CD 1.1 mi. Time CPA 4:54 RS 12 kts. RS 25 kts TC 274° Time CPA 1:10 Time CPA 3:58 TS 1.7 kts. TC 186.5° TC 153° New course 8.5° TS 19-9 kts. TS 21.4 kts New speed 5-3 kts. New course 165° New course 53° New CD 6 mi. New speed 12.4 kts. New speed 13 kts New RS 10.3 kts. New RS 8.4 kts. New RS 29 kts New CD 2.4 mi. New CD 2.7 mi. 6-25 PROBLEM 7 PROBLEM 8 PROBLEM 9 CPA CPA CPA .8 mi. RS 8 kts. RS 7.8 kts. RS 7-1 kts. Time CPA 8:15 Time CPA 6:17 TC 330° TC 319.5 TC 109. 5 ( 3 TS 11 kts. TS 8.6 kts. TS 10 kts. NS l.k kts. Prob. A Prob. A New CPA New CPA New RS 3.2 kts. New RS 9.6 kts. Prob. B Prob. B New CPA 1.5 mi. New CPA 1 mi. New RS 12 kts. New RS 12.6 kts. New speed 5 kts. New speed 3.7 kts. New CD 2.1 mi. New CD l.k mi. PROBLEM 10 PROBLEM 11 PROBLEM 12 CPA 1 mi. CPA .9 mi. CPA .25 mi. CD 2.5 mi. RS 16.5 kts. RS 22 RS 2k kts. TC 316.5° TC 25° TC 117° TS 15 kts. TS I6.5 kt-s TS 13.8 kts. 12° New course 261° New course 1430 New course New speed 8.9 kts PROBLEM 13 PROBLEM Ik PROBLEM 15 CPA . 5 mi. CPA .6 mi. CPA .6 mi. RS 18 kts. RS 10 kts, CD • 7 mi. TC 68° TC 18.5° RS 6 kts. TS 15 kts. TS 10.4 kts. Time s CPA 11:30 New course @ 15 kts. 355 New course 67° TC 319. 5° New speed 9.8 kts. TS New New New course speed CD 8.3 kts. 230 7-5 kts. 2.5 mi. 6-26 CHAPTER 7 - RAPID RADAR PLOTTING Section 7.1 - DEVELOPMENT OF RAPID RADAE PLOTTING Written by - Commander Edward F. Oliver, USCG as published in U. S. Coast Guard Proceedings of the Merchant Marine Council - March 1969 THE YEAR 1969 may be a landmark year in the maritime world- -the year that deck officers stow away maneuvering board and plotting sheet pads and commence practical plotting directly on the radarscope or reflection plotter. Just as the time sight method to find longitude gave way to H„0. 2l4, it appears that the conventional naval combat information center (CIC) speed- triangle method of plotting, where radar furnished information is transferred to a maneuvering board for solution, will give way to the distance- triangle method. The latter method will be designated for the purposes of this article as the rapid radar plotting method where the plot is made directly on the radarscope. In the conventional CIC speed- triangle method the magnitudes of the vectors represent the speed in knots to a scale convenient to the navigator, whereas in the rapid radar plotting method the relative plot and vector diagram are combined and the magnitudes represent the actual distance traveled during the plotting interval. MAJOR DIFFERENCES The major difference between the two methods is that in the rapid radar plotting method the vector diagram may be plotted at the location of the target echo on the radarscope (or on a plotting sheet if desired). In effect this method lends itself to solution directly on the scope 7-1 because there is no clutter of solution lines overlapping at the center of the scope. Most importantly several targets can "be plotted at the same time and evaluated together in aspect. Although the vector diagrams are smaller than the CIC speed- triangle method, and some accuracy is sacrificed, the rapidity of solution and the fact that several targets can be plotted at the same time more than compensates for the accuracy sacrificed. The conventional CIC-maneuvering board method was fine for the naval officer with a gang of white hats in the CIC shack, but for the harried merchant marine deck officer navigating with limited visibility in traffic the value is questionable. The CIC method was designed for U. So naval vessel station keeping and to plan tactical maneuvers for some future time, not to determine the CPA, true course and true speed of a meeting vessel. Unfortunately, for too long, the shipping industry, with a few excep- tions, ignored the inadequacy of the conventional CIC method. The fact that the navigating personnel on watch on a merchant ship number one or two as opposed to the four, five, or six on watch on a naval vessel was ignored. It was assumed that somehow the mate would be able to take radar ranges and bearings of various targets, transfer the information to a maneuvering board, make the proper mental calculations in applying different distance and speed scales, keep a visual watch, answer the telephone, make log and bell book entries, etc. The fact is that while the merchant marine deck officer is a capable man, he is still only human and has certain limitations. 7-2 MULTIPLE TARGET INADEQUACY The time has come when the merchant marine deck officer, and all those interested in his performance- -he they steamship owners or admiralty attorneys—are realizing that the CIC method of plotting may not be serving him properly and may in fact poorly serve him. The question- able adequacy of the CIC method is no better illustrated than in the multiple target situation. It is necessary to use a separate plotting sheet for each target or different colored pencils which is subject to error at night because otherwise the vector diagrams plotted at the center of the plot would overlap and the clutter of lines would be confusing. With each target plotted on a separate sheet, it is difficult to base an evaluation of the effect of own ship's change of course on several targets and have an appreciation of the aspect of the overall problem. Example 22 in H.O. 217, Maneuvering Board Manual , 1963 edition, is an excellent example of the excessive amount of work and time required in the solution of a multiple radar target situation through the use of separate relative plots and speed triangles. Eventually the time will come when radar sets will be equipped with computers which will automatically read out multiple targets' true courses and speeds, CPAs, and a recommended change in own ship's course and/or speed. However, in the interim, until vessels are equipped with such computers, it is the deck officers' responsibility to determine the required information in the minimum of time. A simpler and more rapid method than the CIC method is mandatory, and the rapid radar plotting method may be the interim solution until the marine computer era arrives. The rapid radar plotting method is most effective if made directly on 7-3 the radarscope or reflection plotter. However, if the radar is not equipped with a reflection plotter, and the diameter of the scope is too small to allow for plotting, the method can still be used to better advantage on a maneuvering board than the speed- tria ngle method. Although the disadvantages associated with the transference of data and the changing of distance scales are still present, multi- ple targets can be plotted on the same plotting sheet and an evaluation made of a contemplated course change with an aspect of other targets available. This is not feasible using the CIC method, where plotting multiple targets introduces confusion and errors. The main limitation to efficient use of the rapid radar plotting method is the diameter of the radarscope. Ten inches appears to be the practical lower limit for use of the method, and with a 10-inch scope the range must be relatively low, approximately 8 miles. If plotting is done at a greater range, the vector diagram will be too small for an acceptable tolerance in the estimate of course and speed. The use of the rapid radar plotting method has been advanced occasionally in the past few years by a few discerning navigators but only recently has its true worth over the CIC method been fully appreciated. The method has been called by various names such as the di stanc e- triangle technique, the Keystone method, the Slack method, the Newmar method, and the British method. It is understood that this method is now widely used in the British merchant service. MAIN ADVANTAGES The following is a recapitulation of the advantages of the rapid radar plotting method: 1-k (1) Construction of the vector diagram at the respective target echo provides a better presentation of target aspect. (2) There is less overlapping of vector diagrams and thus less confusing clutter. (3) Essentially only one scale is necessary for the target solution, i.e., the distance scale of the radar range setting. (h) There is no need to calculate the relative speed; a reasonably accurate estimate of the relative speed may be made by comparison of the length of the relative vector with the length of own ship's true vector which is directly proportional to own ship's speed in knots. (5) The method is the basis of a very rapid means of analyzing the effects upon the relative movements of several radar targets which would result from an intended course of action by own ship. Editor' s Note - The Coast Guard is contemplating rules concerning simulator training, as well as rules requiring a deck officer to pass a radar plotting examination when renewing his license. However, the latter rules would permit the deck officer to substitute simulator training for the plotting examination. 7-5 CHAPTER 7 - RAPID RADAR PLOTTING Section 1.2 - RADAR PLOTTING SHEET - 4665 SERIES PRELIMINARY: Any of the radar plotting problems can "be solved by use of a simple compass rose; or indeed, by protractor on plain paper. The RADAR PLOTTING SHEET, 4665 SERIES was designed to facilitate the plotting of radar contacts so that rapid and accurate estimates can be made of the elements associated with an encounter between two or more ships. PLOTTING AREA: The plotting sheet is designed to resemble the appearance of a typical radar scope. The compass rose represents degrees, true. Concentric circles suggest the fixed range rings on many radar scopes. Radars differ in the number of range settings available, and in the number of fixed range rings shown on these settings. In general, however, four range rings will be seen at the commonly used 20-mile range setting. If the radar has a 15-mile range setting, only three range rings will usually be seen. However the DISTANCE relationship between range rings remains the same: 20 miles - 4 range rings = 5-mile intervals. 15 miles - 3 range rings = 5-mile intervals. If the radar range setting is 15 miles, the three INNER circles of the plotting sheet correspond to the three range rings on the radar scope. Similarly, if using the 6-mile scale, only the three inner circles of 7-6 the plotting sheet are used, at 2-mile intervals. THE DISTANCE SCALES: Four distance scales are provided near the left-hand "border of the plotting sheet. These are for measuring distances depending on the scale in use. For this method of plotting, the speed scales located near the right-hand border are not used. 7-7 CHAPTER 7 - RAPID RADAR PLOTTING Section 7.3 - DISTANCE TRIANGLE METHOD - "A" DETERMINATION OF CLOSEST POINT OF APPROACH (CPA): (1) Draw Own Ship's true course from center (e) to outer edge of plotting sheet and label Own Course (OC). (2) Plot range and true bearing of the contact ship as observed on the radar scope, label Ml, M2, M3, etc., and record the time of each. (Six minute intervals will simplify later calculations). (3) Construct the RML from Ml through latest M and extend this line well past center of sheet. Label this line RML and terminate with an arrow. (h) Draw a right angle from the RML to center (e) of the sheet and label point where the right angle joins RML as the CPA. This indicates the Closest Point of Approach and bearing of CPA. Measure this distance and read off on the distance scale. NOTE : Own ship is represented in the center of the sheet and may be illustrated by drawing an outline of a ship, headed on own course line. Clearance, if any, or whether ahead, astern or abeam, depends upon how RML runs in relation to own ship. If RML crosses own course line, this is the crossing distance and indicates how far contact will clear dead ahead. DETERMINATION OF RELATIVE SPEED: (5) Measure the distance between Ml and M2, noting the elapsed time and transfer this distance to the distance scale in use. This 7-8 will establish miles run in the elapsed time between Ml and M2. Compute speed on the logarithmic scale. This is the relative speed. DETERMINATION OF TIME OF CLOSEST POINT OF APPROACH: (6) Measure distance along RML from the last bearing to the CPA and with the relative speed, calculate time necessary for contact to arrive at CPA. Add this time to the time of last bearing. This will be time of CPA. A rapid estimate can be made by stepping off 6 minute increments along the RML from latest M to CPA. THE FIRST VECTOR TRIANGLE DETERMINATION OF CONTACT'S TRUE COURSE AND SPEED: (7) Parallel Own Course (OC) from point Ml (r) and draw line in the opposite direction as Own Course. For purpose of identification, designate this line the "ladder". (8) Using own speed and elapsed time between bearings, compute our distance run using logarithmic scale. (9) From the same scale used in plotting the contact, measure this distance with dividers. Transfer this distance from the first bearing, Ml, and mark distance on the ladder. Label this mark as (e) or as 6 or 12 minutes later than time of first plot (Ml), depending on preferred elasped time between bearings (6 or 12 minutes). This mark may be repeated on ladder for 18 minutes, 2k minutes, etc., depending on how many rungs of the ladder we wish to establish. 7-9 (10) Draw a line from the rung on the ladder (e) which you have selected as the time "between hearings, and connect to M2„ Transfer this line to center of plotting sheet, mark and read contact's true course on azimuth circle. Contact's true speed is obtained by measuring distance from rung on ladder to M2 (m). With measured distance and elapsed time between bearings, determine true speed of contact on the logarithmic scale. THE SECOND VECTOR TRIANGLE DETERMINATION OF OWN SHIP 1 S NEW COURSE OR SPEED TO REDUCE RISK OF COLLISION: (11) Locate point of execution, Mx: This is the contact's predicted position providing it continues to advance along the RML which has been established. Rather than locate Mx by Time Method, it is quicker and more practical to decide at what distance you want the maneuver to take place. As an example, let us say 8 miles. The point of execution (Mx) is the intersection of the 8-mile circle with the RML. (12) Draw a new RML from point Mx tangent to the desired new CPA circle and label RML 1. (13) Using a drawing compass, place pin of compass on ladder rung (e). (Be sure it is the same rung as you used for finding contact' s true course and speed). Place pencil point of compass on Ml. Now draw an arc with the compass. (l^) From M2 draw a line parallel to RML 1 to intersect the arc 7-10 previously drawn. This line may intersect the arc at two points. A line drawn from rung of ladder to the intersection establishes the new course to steer. Transfer this line to the center of the plotting sheet. Mark and read the direction of the new course on the azimuth circle. (15) New speed on original course is determined by measuring distance with dividers from rung on ladder to where line drawn from M2 parallel to RML 1 crosses ladder. The appropriate scale on the side of the sheet will enable us to accurately measure this distance. Using this distance and the elapsed time, own ship's new speed can be determined by means of the logarithmic scale. During conditions of low visibility in the open sea, if possible, a bold course change well in advance should be carried out. At speeds greater than ten knots, plan for a new CPA of at least three miles. Approaches within sound distance should be avoided. (See Rules of the Road, Speed in Fog). Three miles gives a good cushion that allows for inherent errors in the radar, human error and other factors that lend to a smaller CPA than what otherwise might be desired for a safe passage. 7-11 DISTANCE SCALES Radar Range Setting adar Range Setting w 20 J6 PROBLEM *\ SHEET #M RADAR PLOTTING SHEET MILES MttfS SPEED SCALES KNOTS 4665-10 GREEN H 4665 Series Sizes Available 10 inch diameter HO. 4665 10 Green HO 4665 10 Black 15-inch diameter HO 4665 15 Green HO 4665 15 Black BADAR PtOllINt :;mti PRICE 75 rent Per Pad of 50 H. 0.4665-10 GREEN DISTANCE SCALES Rar'ar Range Setting 20 ?6 MILES MILES PROBLEM &\ SUEET#2 20 16-n 19 — 15 — 18 — - - 14 — 17 — - 16 — 13 — 15 12— 14 — ii — 13 — - io — 12 — - 11 — 9 — 10 — 8 — 9 — 7 — 8 — - - 6 — 7 — - 6 5 — 5 — 4-1 4 — 3 — 3 — - - 2 — 2 — " 1 — _ ~o- o- RADAR PLOTTING SHEET SPEED SCALES KNOTS -40 r 60 Radar Range Setting 8 12 MILES MILES 8— il2 Same divider spread- 4665-10 GREEN HO. 4665 Series Sizes Available 10-inch diameter HO. 466510 Green HO. 4665-10 Black 15-inch diameter H.O 4665 15 Green H 0. 4665-15 Black Published at Washington, D. C ! U. S. NAVY HYDROGRAPHIC OFFICE minority ol Ihe SECRETARY OF THE I PRICE 75 cent Per Pad of 50 w H.O. 466540 GREEN DISTANCE SCALES Rad 2o ngeSe J6 8 PROBLEM^' mms Mies SHEET *J5 RADAR PLOTTING SHEET Voyage No... SPEED SCALES 4665-10 GREEN H. 0.4665-10 IT GREEN HO 4665 15 Green HO 4665 15 Black DISTANCE SCALES Radar Range Setting RADAR PLOTTING SHEET :d SCALES KNOTS — 40 60 n any two corresponding quantitie lof third by laying fule thiouch points on pro[ er scales and read intersection on third state 4665-10 BLACK SECRETARY OF THE NAVY j L H.O 2665-10 MANEUVERING BOARD DISTANCE in yards Relative or actual 9SS £ 8 DISTANCE in miles Use of 3 scale nomogram. Given any two corresponding quantities, solve p ■ l 19 — 15 — 18 — 17 — 14 — 16 — 15- 13 — 12— 14 — ii — 13 — 12 — 10 — 1 1 10 — 9 — 8— 9 - 7 — 8 — 7 6 — 6 — 5 — 5 A— 4 3 — 3 — 2 — 2 — 1 1 ►0 — o-i bPEED SCALES KNOTS 4665-10 BLACK Published at Washington, D C. by the . OCEANOCRAPHIC OFFICE under the authority ol the SECRETARY OF THE CHAPTER 7 - RAPID RADAR PLOTTING Section 7-6 - DISTANCE TRIANGLE PROBLEMS - METHOD "B" PROBLEM : A navigator, while steering a course of 0° true at a speed of 11 knots, observes on his radar scope another vessel approaching forward on his starboard beam. At 10:00 a bearing and a range was taken from the radar screen and found to be 60° true at 15 miles. At 10:12 the bearing was found to have changed to 59° true at 12 miles. Since the bearing was not changing very rapidly it is evident that some action will be necessary. By use of the relative plot, find the CPA and time of the CPA. By use of the first vector triangle, find the true course and speed of contact. In plotting, radar bearing #1 will be called Ml, bearing #2-M2, etc. DECISION : The navigator has planned on a danger zone of at least 3 miles. By use of the second vector triangle, what course change should be made when the range decreases to 9 miles for the contact to clear ahead, in minimum time, with a CPA of 3 miles? Point of course change will be called the point of execution. ANSWERS : Closet Point of Approach The Relative Speed Our Distant Run In 6 Minutes True Speed True Course Our Navigator's New Course The New Relative Speed 7-27 PROBLEM NO. 1 Own course 340° True, 12 kts, TIME BRG. T RANGE Ml 4:12 320° 10.7 mi. M2 4:18 321° 8.4 mi. DECISION: Find course change necessary to clear port to port with 3 mile danger zone. Time of course change 4:24. ANSWERS Closest point of approach True course True speed New course PROBLEM NO. 2 Own course 252° True, l6 kts. TIME BRG. T RANGE Ml 3:10 195° 12 mi. M2 3:22 194° 8.7 mi. DECISION: Find new course for contact to clear astern with danger zone of 2 miles. Course change 3:34. ANSWERS Closest point of approach True course True speed New course PROBLEM NO. 3 Own course 350° True, 18 kts. TIME BRG. T RANGE Ml 3:00 280° 9 mi. M2 3:10 279° 7 mi. DECISION: Find new course for contact to clear astern with danzer zone of 2 miles. Course change when range drops to 5 miles. ANSWERS Closest point of approach True course . . . . True speed New course PROBLEM NO. 4 Own course 10° True, 9 kts. TIME BRG. T RANGE 9:55 89° 7-5 mi. mi. ANSWERS Closest point of approach True course True speed New speed Ml M2 10:17 86 u 4, DECISION: Speed change necessary, maintaining same course, for target to clear ahead with danger zone of 1.5 miles. Speed change at 10:28. 7-28 PROBLEM NO. 5 Own course 70^ True, l6 kts. TIME BRG. T RANGE Ml 3: ;06 15° 10, .8 mj. M2 3: :12 16° 8, • 3 mi M3 3: :18 17° 5- ■ 9 mi ANSWERS Closest point of approach Time closest point of ap- proach True course True speed New speed DECISION: Speed change necessary, maintaining same course, for contact to clear ahead with danger zone of 3 miles. Speed change when range drops to 5 miles. ANSWERS Closest point of approach True course True speed New course at 15 kts PROBLEM NO. 6 Own course 342° True, 11 kts. half (full 18 kts. ) TIME BRG. T RANGE Ml 9:06 287° 12 mi. M2 9:12 287° 10.2 mi. M3 9:18 288° 8.4 mi. DECISION: New course required for contact to clear astern with danger zone of 2 miles. We are increasing speed to full with a mean build up of 15 knots. Time of course and speed change 9:24. PROBLEM NO. 7 ANSWERS Own course 35 True, l4 kts. Closest point of approach Time closest point of ap- TIME BRG. T RANGE proach True course Ml 11:00 50° 10.3 mi- True speed ZZZZZI M2 11:05 49° 8.4 mi. New course DECISION: Find new course for contact to clear ahead (port to port), with 3 mile danger zone. 7-29 PROBLEM NO. 8 Own course 20° True, 7 kts. TIME BRG. T RANGE Ml 7:00 M2 7:15 90° 10 mi. 90° 8 mi, Problem A If our course was changed to 3^-0° at 7:30, what would he the result? Problem B If our course was changed to 60 at 7:30, what would be the result? PROBLEM NO. 9 Own course l60° True, 5 kts. TIME BRG. T RANGE Ml 5:00 260° 10 mi. M2 5:10 260° 8.7 mi. Problem A If our course was changed to 180 at 5:20, what would be the result? Problem B If our course was changed to 220° at 5:20, what would be the result? PROBLEM NO. 10 Own course l80° True, l6 kts. TIME BRG. T RANGE Ml 6:06 M2 6:lk M3 6 : 18 182° 18 mi. 182.5° 13.2 mi. 183' 10.8 mi ANSWERS Closest point of approach Time closest point of ap- proach True course True speed Problem A New closest point of ap- proach Problem B New closest point of ap- proach ANSWERS Closest point of approach True course True speed Problem A New closest point of ap- proach Problem B New closest point of ap- proach ANSWERS Closest point of approach True course True speed New course DECISION: Course change to clear port to port with danger zone of 3 miles. Course change when range decreases to 7 miles. 7-30 PROBLEM WO. 11 Own course 310 True, 13 kts. TIME BRG. T RANGE Ml 1: :00 330° 16 mi. M2 1: :10 333° Ik mi. M3 1: ;20 337° 12 mi. PROBLEM NO. 12 Own course 52° True, 15 kts. TIME BRG. T RANGE Ml 5: :k0 52° 14. ■ 9 mi. M2 5: ■k6 52° 11, ,6 mi. M3 5: :52 52° 8, ■ 3 mi. ANSWERS Closest point of approach Time closest point of ap- proach True course True speed ANSWERS Closest point of approach True course True speed New course DECISION: Course change to clear port to port with 3 mile danger zone. Course change when range decreases to 6 miles. PROBLEM NO. 13 Own course 230° True, 16 kts. TIME BRG. T RANGE 6:00 250° 6: 06 255° 10 mi. 7 mi- Problem A Course change required to clear starboard to starboard with danger zone of 3 miles. Course change at 6:09. Problem B If we stopped our vessel at 6:09, what would be the result? ANSWERS Closest point of approach Time closest point of ap- proach True course True speed Problem A New course Problem B New closest point of ap- proach 7-31 PROBLEM NO. ik Own course 20° True, 18 kts. full, (half 10, slow k kts. ) TIME BRG. T RANGE ANSWERS Closest point of approach True course True speed 3:00 3:10 80° 80° 12 mi 10 mi, Problem A Problem A Course change necessary for contact to New course clear ahead, changing to the right, with danger zone of 3 miles. Course change when range decreases to 6 miles. Problem .B Problem B Speed change necessary, maintaining Telegraph order same course (20°), for contact to clear ahead with 3 mile danger zone. Speed change when range decreases to 6 miles. What telegraph order shall we give? PROBLEM NO. 15 Own course 50° True, 9 kts. half, (slow 6, full 15 kts. ) TIME BRG. T RANGE 4: ;06 20° 10 mi. h: :12 20° 8 mi. h: ;18 20° 5. S mi ANSWERS Closest point of approach True course True speed New course/ speed DECISION: Our danger zone 2 miles. We hang on until range decreases to h miles. The decision is ours. What shall we do? Work out solution, then see answer. 7-32 ANSWERS PROBLEM NO. 1 PROBLEM NO. 2 PROBLEM NO. 3 CPA • 5 mi. CPA • 5 mi- CPA .6 mi. TC 115° TC 316.5° TC 30° TS 12.9 kts. TS 15 kts. TS 17 kts New course 31° New course 282° New course 11° PROBLEM NO. k PROBLEM NO. 5 PROBLEM NO. 6 CPA .8 mi. TC 330° TS 11 kts. New speed 7-6 kts. PROBLEM NO. 7 CPA • 9 mi. Time CPA 11:27 TC 260° TS 11 kts. New course 70° CPA . 5 mi. CPA .k mi. Time CPA 3:32 TC 68° TC 153 TS 15 kts TS 21.5 kts. New course 6° New speed 3 kts. PROBLEM NO . 8 PROBLEM NO. 9 CPA Time CPA TC TS Prob. A New CPA Prob. B New CPA 8:15 319° 8.6 kts. 1.5 mi, CPA TC TS Prob. A New CPA Prob. B New CPA 109-5° 10 kts. 1 mi. PROBLEM NO. 10 CPA . 5 mi. TC 1° TS 20.1 kts New course 2^5° PROBLEM NO, ■ 13 CPA 1.9 mi. Time CPA 6:19 TC 68° TS 15-4 kts Prob. A New course 206° Prob. B New CPA 1.1 mi. PROBLEM NO. 11 CPA 5-5 mi, Time CPA 2:10 TC NONE TS D.I.W. PROBLEM NO. 12 CPA TC TS 232° 18 kts. New course 118 PROBLEM NO. ik CPA TC 3^0° TS 16 kts. Prob. A New course 69° Prob. B Tel. order slow, using propeller wash to accelerate reduction When bearing starts to change, ring half Exact new speed 12 kts. 7-33 ANSWERS PROBLEM NO. 15 Clear contact astern ( tc port), change course to 100° raising to full speed. 15 minutes is required to build up to full, thus using a mean of 13 knots. Possibly our navigator would prefer to stop ship. This might be somewhat dangerous. Let us analyze the problem. First plot situation as our contact sees it. We may use the same plot. TARGET'S COURSE 180° Ik kts. Ml (us) k:06 200° 10 mi. M2 4:18 200° 5-9 mi Now from the contact's view point, his logical change is to the right and unless he changes more than k0° he would enter our danger zone. If we stopped ship, steerage way should be maintained keeping bow on, thus presenting a smaller obstruction. NOTE: For further information regarding plotting problems, refer to: Practical Radar Navigation, Hengst, 1958 edition of Bowditch, Practical Radar Plotting by Thayer or Oceanographic Office Publication No. 257- 7-3 1 * CHAPTER 7 - RAPID RADAR PLOTTING Section 7-7 - TRUE MOTION HOW TRUE MOTION RADAR WORKS "Courtesy of Radio Corporation of America" The development of TRUE MOTION radar in recent years represents a significant advance in the science of navigational radar. To anyone familiar with the operation of both RELATIVE and TRUE MOTION radars, the advantages inherent in TRUE MOTION are obvious. On RELATIVE MOTION radars, the picture presented is a continuous study of relative motion where your ship and other ships (the "targets") are moving. Fixed objects also move on the picture because of your own movement. The one thing fixed on the picture is you; you are always at the center of the picture. Thus, in relative motion, the captain must first evaluate the situation and then plot those targets which are a potential danger and take corrective action if required. Page 7-37 shows a typical RELATIVE MOTION radar plot. In TRUE MOTION radar, the face of the cathode ray tube becomes an area-- a chart--where fixed objects do not move and all moving objects, including one's self, move at their own rates. Moving targets have tails caused by the long persistence of the phosphor. These tails, or trails, indicate heading, and their length when compared to one' s own trail is a measure of speed. If properly used, TRUE MOTION can eliminate perhaps 95 percent of the need for plotting. Answers such as distance of closest approach and 7-35 distance or time of crossing, however, are more easily obtained from REIATIVE MOTION. The usual practice in providing TRUE MOTION is to north stabilize the picture; i.e., the top of the picture is always north, and everyone moves according to his true course. Thus, if you are moving south 180 degrees, you are actually moving down. Objects seen on the left of the scope are "out of the right window" and objects on the right are actually on the left. Page 7-38 shows a typical TRUE MOTION radar picture. This necessitates some mental inversion for proper navigation. Generally, in commercial navigation, skippers prefer to see their vessel move up on the scope, so that echoes on the left are from objects on the left or port side and echoes on the right are from objects on the right or starboard side. In the equipment described here, moving up is automatically provided although it is not a primary requirement of true motion. This is done by first north stabilizing the picture and then automatically rotating the cathode ray tube assembly so that one's own movement is always up. Zero on the azimuth scale around the tube is always north. The scale reading at the top of the scope is your true heading. Thus, if this were 180 degrees--you would be traveling south, but the picture is oriented so you move up- -the "True View." The advantage of this type of display can be seen graphically on page 7-39* 7-40 and 7-Ul. 7-36 70- — 90 180 FIG. 1 — Radar plotting, relative motion, 16- mile range. Own Ship Speed, 18 knots Observed Ship, first plot at A, 10 miles, 33 degrees Second plot at B, 6 minutes after A, 1.4 miles Third plot at C, 6 minutes after B, 1.4 miles AX = own ship movement in 12 minutes, 3.6 miles AC "— apparent course, XC = actual course, 310 degrees DZ = crossing point, 2.6 miles EZ = closest approach point, 1.8 miles Relative speed = AC = 2.8 m. in 12 min. = 2.8 x 5 = 14 knots CD = 5.2 miles at 14 knots = 22 minutes Courtesy of RADIOMARINE CORP. 7-37 NORTH 270 - 180 Fig. 2 -TRUE MOTION with north stabilized picture shows one's own ship on heading of 90 degrees. Courtesy of RADIOMARINE CORP. 7-38 90 « PfSFT OTHER SHIP 16 MIN /■■/■•'■// /''■'/"' 7 30 MIN, , U / ' / / i i r i 24 MInA, / I / Y/ ' /• ' 18 MIN 12 MIN ■ 1/ / 6 MIN« / 180 U> ONES OWN SHIP 270 Fig. 3 — RCA TRUE MOTION, showing posi- tion every 6 minutes of one's own ship and one other vessel. Own ship speed: 10 knots at 90 degrees. Other ship: 10 knots at 345 de- grees; will cross bow in 24 minutes at 2.5 miles. Range scale, 6 miles; view ahead, 9% miles; travel time, 50 minutes before reset at 10 knots. Courtesy of RADIOMARINE CORP. 7-39 HEADING FLASH 45 ' s / / ' j / / . - / ELECTRONIC CURSOR SHOWS • CONSTANT RELATIVE J BEARING V^LAND,-", f 270 \ 180 Fig. 4 -RCA TRUE MOTION, showing posi- tions every 5 minutes of typical collision course. Own ship speed: 12 knots at true course 45 degrees. Other ship: 18 knots at true course, 277 degrees. Range scale, 6 miles. Courtesy of RADIOMARINE CORP. 7-40 HEADING FLASH 90 97 4-BUOYS — 180 270 Fig. 5 — Picture at T — 10, after own ship turned 52 degrees to starboard to avoid col- lision and enter channel. Own ship speed: 12 knots at true course 97 degrees after turn. Other ship: 18 knots at true course 277 de- grees. Range scale, 6 miles. Courtesy of RADIOMARINE CORP. 7-41 CHAPTER 8 - DIRECT/REFLECTION PLOTTING Section 8.1 - TOOLS AND EQUIPMENT The distance triangle method of radar plotting is achieving wide pop- ularity among radar observers who have become adept at direct plotting; that is to say, plotting directly on the concave plotting surface located above the Plan Position Indicator. All radars are not equipped with such a device. In addition to being fitted with special devices in order to make direct plotting possible, certain special plotting tools are also required to accomplish this end. Unfortunately, to date there are no standard plotting tools available which are qualified for direct plotting. It is necessary for the radar observer to improvise his own plotting tools for this purpose. The following information may be of some value in developing direct plotting tools. GREASE PENCIL : Another name for the grease pencil is china marking pencil, which means that it is capable of writing on glass or china. Any other type of pencil offers disadvantages. The marks made on the reflection plotter can be wiped away with a clean soft cloth. Bear in mind that the surface of the reflection plotter is made of glass or plastic material and is easily scratched. It is possible to purchase a special cream for cleaning plastic such as that which the MANUFACTURER provides for this purpose. It acts as a solvent for cleaning grease marks and will not damage the plastic plotting surface. China marking pencils may be purchased in a number of colors, in the 5 & 10 cent stores - red or yellow being the most suitable. Through hard usage in the radar school, it was found that the mechanical or refillable type of pencil served better than the wooden variety that, required constant sharpening. USE OF THE GREASE PENCIL - DETERMINATION OF CPA : Caution is required to plot with accuracy directly on the reflection plotter. The grease pencil is soft, easily broken, and will skip unless marks are drawn rapidly. In order to plot bearings properly, press pencil point against plotting surface close to the contact, observing where point reflects on transparent mirror (mirror is located just above the Plan Position Indicator), release pressure slightly and mark rapidly across contact. Follow same procedure a second time marking a fine X with contact in center of the X. If possible, plot bearings every three minutes, marking the time on at least the first bearing. Fair a line thru plot marks with rule, press pencil lightly against rule and draw rapidly, making fine RML. Variable range marker may be used to measure CPA. The RML should be revised if contact does not follow the original relative movement line. PLASTIC RULE : A six or eight inch flexible, clear plastic rule is used to draw relative movement lines, course lines, etc. It can also be utilized for marking distances when properly calibrated. 8-2 CALIBRATING PLASTIC RULE : Switch radar to 15 or 20-mile range. Crank variable range marker out to an optional starting point of 5 miles. At the junction between variable marker and ship' s heading flash, parallel to variable marker, draw a small line. Follow same procedure for our distance run at 6 and 12-minute intervals. You will now have three marks on plotting surface. Lay rule alongside marks and transfer plotting marks to rule. Six-minute runs are useful due to the fact 6 minutes is divisible into an hour by ten, thus simplifying distance run calculation, EXAMPLE: At 15 knots, our distance run is 1.5 MILES IN 6 MINUTES. For practical application at night when grease pencil marks on rule will not show clearly in the dark, the rule's edge may be notched for standard speeds. DIVIDERS : As was mentioned earlier, the glass or plastic surface of the plotter is easily scratched, therefore, it is impractical to use sharp points of dividers that will mar this surface. The partial answer to this problem would be RUBBER TIPPED DIVIDERS. 5-3 CHAPTER 8 - DIRECT/REFLECTION PLOTTING Section 8.2 - REFLECTION PLOTTING DETERMINATION OF CONTACT'S TRUE COURSE AND SPEED 1. Adjust parallel line bearing cursor parallel to ship's heading flash. Lay calibrated rule on Ml parallel to cursor lines. 2. Draw own ship's true (course-speed) vector to end at Ml. The length of this vector is equal to the 6 or 12-minute run calibrations on the rule, as the case may be. 3- Two sides of the distance vector triangle have now been formed. One side is the segment of the RML between plots Ml and M2; the other side is own ship's course and distance run in the elapsed time between plots Ml and M2. On completing the triangle, the third side represents the contact's true course and distance run during the elapsed time between plots. h. The contact's speed may be estimated by comparing the length of its true (course- speed) vector (the third side) with the second side, the corresponding speed of which in knots is known. 5. The contact's true course may be read by setting the parallel line cursor parallel to the contact' s true (course- speed) vector. DETERMINATION OF OWN SHIP' S NEW COURSE OR SPEED TO REDUCE RISK OF COLLISION 1. The predicted Mx (Point of Execution) position should be located 8-1* on the RML. The most practical direct plotting method is to choose some distance off, such as 8 miles, rather than plot Mx on the "basis of time.. 2. Set variable range marker to 8 miles. Designate Mx where it intersects the RML. 3- Using a fixed range ring or by setting the variable range marker to the desired CPA, draw the new RML 1 from Mx tangent to the circle described by the variable range marker. From Mx, two lines can be drawn tangent to the circle described, depending upon whether the contact is to pass ahead or astern. Using the parallel line cursor as an aid, draw a line parallel to RML 1 through M2. k. Rotate own ship's true (course-speed) vector (er) about its origin to intersect the line drawn through M2 parallel to RML 1. A measuring device such as a small plastic rule or rubber tipped dividers may be used as an aid in rotating the vector. 5. When the contact's speed is greater than that of own ship, there may be two intersections formed in rotating own ship's true (course- speed) vector (er). The intersection farthest from M2 results in the highest relative speed, and is selected, generally, in order to expedite the safe passing. 6. A vector drawn from the origin of own ship's original true (course- speed) vector (er) to the appropriate intersection provides the new true (course- speed) (er l) vector required for the evasive action. Again, the parallel line cursor may be used to read own ship' s new course. 8-5 7« If it is desired to take evasive action "by speed change only, the new speed is established at the intersection of the line drawn through M2 parallel to the new RML 1 with own ship's true (course-speed) vector (er 2)„ The new speed is represented by the length from the origin of the original true vector to the latter intersection, the length between e and r 2. 8-6 CHAPTER 9 - RADAR SIMULATORS Section 9.1 - DEVELOPMENT OF MARINE RADAR SIMULATORS For more than twenty years, radar has been a shipmate on merchant vessels and during this period the electronics industry has made many advances to improve and simplify their respective equipment. With modern radar on virtually every ship, collisions continue to occur which could have been avoided, had the ship's officers made proper use of this valuable aid. This brings up an old question that is still asked following every collision between radar equipped vessels during periods of low visibility. "How can this happen?" Of course, one answer is that radar alone cannot prevent collisions. We also know that these in- cidents happen during daylight and clear weather and that they will probably continue. Only through improved training and experiences gained by Deck Officers through the employment of Radar Simulators, can both clear and foul weather collisions be drastically reduced or avoided. As early as 1955; the British Ministry of Transport recognized the value of developing an instrument which could simulate a radar picture as would be received on a ship' s radar, developing a prototype in 1957 • The first simulator course was presented in 1959> and with its intro- duction and rapid expansion more than twenty simulators have been in- stalled in Europe in the last ten years and only five in the U. S. Simulators range from Analogue one "own ship" with two moving targets to a digital computer two "own ship" with four moving and six stationary targets. 9-1 There is a saying attributed to old sea dogs, that "There is no substitute for sea experience". All things considered, it would be most impractical to attempt the colossal task of training merchant marine Deck Officers, and in particular, prospective Deck Officers, in the rudiments of radar observing, at sea . Through the combined efforts of the U. S. Maritime Administration and the U. S. Coast Guard, it was expected that through the training programs offered by the Maritime Administration shore- side Radar Schools the in- cidence of collision involving radar equipped vessels, would be drastically reduced. After 10 years of working toward this goal, the collision alarm sounds louder than ever. It becomes immediately apparent that a flaw still exists in our effort to curtail the APPALLING collision rate. The QUESTIONS then remain, where is the flaw and how do we best attack it? THE FLAW: After carefully analizing these questions and reviewing studies conducted by the U. S. Coast Guard, it was found that many qualified Deck Officers do not plot at all. When the safety of life and property are willfully abused by those men who have the responsibility of protecting the rights of others, then it becomes wanton negligence. Every licensed Deck Of- ficer should be thoroughly acquainted with the Rules of the Road and whether it be International or Inland, he should know verbatum, the "Rule of Good Seamanship". Rule 29/Art. 29: Nothing in these rules shall exonerate any vessel, or the owner, master or crew thereof, from the consequences of any neglect to carry lights 9-2 or signals, or of any neglect to keep a proper lookout, or of the neglect of any precaution which may "be required "by the ordinary practice of seamen , or by the special circumstances of the case. THE ATTACK: In order to create a greater awareness within the U. S. Merchant Marine industry of the responsibility that must be assumed by seamen in this regard, the U. S. Maritime Administration has begun a large scale up- grading program in the area of radar training. If there is no substitute for sea experience and no practical way to train men at sea at this time, then we must bring the sea to the land based Radar Simulator Schools. 9-3 Many maritime nations, in recognizing the importance of this form of collision avoidance training, are currently utilizing radar simulator equipment with a view toward developing highly skilled radar observers. The following is a partial list of maritime radar simulator installations in Europe: MARITIME RADAR SIMULATOR INSTALLATIONS IN EUROPE l) United Kingdom Glasgow Hull Liverpool London, Sir John Cass College South Shields Cardiff Southampton Usage Masters and Senior Officers (preferably Certificate. ) Senior Officers Senior Officers Senior Officers Senior Officers Senior Officers Senior Officers Type Solartron 1+5 targets Ultra 1 own ship 5 targets Ultra 2 own ship h targets Redifon 1 ' own ship 5 targets Redifon 1 own ship 2 targets Ultra 1 own ship 5 targets UNKNOWN 2) Holland Amsterdam Rotterdam Both Senior Officers and Radar Observer course Both Senior Officers and Radar Observer course Ultra 1 own ship 5 targets Ultra 1 own ship 5 targets 9-k 3) Germany Bremen Officers, Masters and normal training courses in future Redifon 1 own ship 2 targets k) Denmark Marstal College Fans College Copenhagen Svendborg Senior Officers and Radar Observer course Senior Officers and Radar Observer course Senior Officers and Radar Observer course Senior Officers and Radar Observer course Ultra 1 own ship 2 targets Ultra 1 own ship 2 targets Redifon 1 own ship 2 targets Redifon 1 own ship 2 targets 5) Norway At least five schools 6) Belgium Antwerp Nautical College Senior Officers and Radar Observer course Senior Officers and Radar Observer course UNKNOWN Redifon 1 own ship 2 targets 7) Sweden Gothenborg Nautical College Stockholm Nautical College 8) France Le Havre Senior Officers and Radar Observer course Senior Officers and Radar Observer course Senior Officers and Radar Observer course UNKNOWN UNKNOWN UNKNOWN 9-5 9) Italy Genoa Senior Officers and UNKNOWN Radar Observer course 9-6 CHAPTER 9 - RADAR SIMULATORS Section 9.2 - USE OF RADAR SIMULATORS Regardless of the type simulator employed, the primary purpose is to advance and perfect the operational aspect of Radar Navigation to the degree of efficiency that radar equipment has attained. The simulator provides the tool that makes it possible to accomplish this goal. It is possible thru the use of simulation to bring real life "at sea situations" into the classroom and demonstrate to Deck Officers the many and varied problems that would be impractical or impossible to set up in actual practice. There is little or no transition from the simulated radar problem to a like situation at sea. The knowledge and experience gained in a few days in the simulator course exceeds that which could be obtained at sea during several years of sailing. The end result, a radar observer that is confident in the radar's capability and in his ability to plot and solve solutions in the most complex radar situation. Additionally, one of the greatest benefits to be gained from radar simulator training is the value gained in bringing together Masters and Mates and the exchange of opinions, ideas, and experiences. By closer international coordination between direc- tors of radar schools, radar information gained through teaching ex- perience can be consolidated and universal procedures and practices standardized for simulator schools to cover any situation that could develop while underway. Such approach would virtually eliminate col- lisions resulting from one vessel counteracting the action taken by the other vessel, where both Masters have been schooled in standard 9-7 radar maneuvers in accordance with the Rules of the Road and the Appendix to the Rules. The effectiveness of Radar Simulators depends upon several factors. One of the most important is the instructor. Simulators basically provide the same information; coast line presentation, target and own ship relationship, with controls for changing each own ship speed and course by the student and like controls for the instructor to maneuver the contacts. "Own ship" is an expression describing a radar set up that will display a radar picture as would be seen if installed on the bridge of the students vessel. Each "Own ship" includes an operational radar, a set of controls, separate from the radar, that controls the speed and course of the ship simulated. By using these controls the Master will be able to maneuver his vessel which will affect the display in exactly the same way as if he were actually on board. The maneuvering characteristics of the vessel simulated are set into the program and the Master of "own ship" is in- formed as to the size. In course and speed change, the vessel will react according to the type vessel being simulated. Rudder delay and turning rate is more realistic by being affected by speed and amount of rudder used; speed control is variable between to 25 knots ahead and to k knots astern. The stopping time is according to the characteristics of the vessel being simulated. Other conditions placed into the problem includes yaw. This control allows a range of yaw and a variable rate of swing. Current can also be set into the problem with the instructor controlling the set and drift. This feature is especially effective when used in conjunction with the coast line display to demonstrate 9-8 coastal currents relative to the land. The land display is a realistic portrayal of an actual radar picture displaying intensity and fore- shadowing of radar targets. The display must include funnel and mast blind spots and sea clutter to simulate sea conditions. One facility considered of vital importance is the Freeze Control, by which all movement of "own ship" and targets can be stopped at any time for a detailed examination of the developing situation. Comments from experienced Masters verify the belief that attendance in a Radar Simulator Course should be mandatory for all Deck Officers and the cost of such training is insignificant when compared to even a minor collision, especially when accompanied by loss of life. 9-9 CHAPTER 10 - APPENDICES APPENDIX A - GLOSSARY Amplify - To amplify is to increase the strength of a radio signal or echo. Antenna - A conductor or system of conductors for radiating or receiving radio waves. Anti -Clutter - A means for reducing or eliminating interferences from sea return and weather. Attenuation - A decrease in the strength of the signal because of the radio wave traveling a given distance or as a result of purposely reducing the signal by artificial means. AFC - Automatic Frequency Control is a means for automatically pre- venting drift in radio frequency. Maintains receiver on the correct frequency. Azimuth - Angular position or "bearing, in a horizontal plane, measured from a zero degree relative to true or magnetic north to the contact in a clockwise direction from to 3^0 degrees. Azimuth- Stabilized PPI - A PPI presentation in which 12 o'clock on the tube face is always made to represent true north, irrespective of equip- ment orientation at an operating position. Bearing - The direction of the line of sight from radar antenna to contact. Bearing Cursor - Mechanical bearing line on PPI for reading contact bearing and/or course. Blind Zones - Areas in which echoes cannot be received. Cathode Ray Tube (CRT) - The radar scope or the picture tube where a stream of electrons are directed against a florescent screen on the face of the tube light is given off at the point the electrons strike the tube face. Clutter - Radar echoes reflected from heavy rain, snow, sea return, etc., which may cause obscurement of relatively large areas on the radar scope. Contact - Any object which will reflect a sufficient amount of signal which will appear on the indicator. Contrast - The difference in the intensity of the light between contact indications and background of the screen. Crystal - A small tube containing a thin wire and a crystalline substance which allows electrical current to pass only in one direction. 10-1 Definition - The detail with which more than one contact at approximately the same range or bearing can "be separated. Echo - The signal reflected "by a contact (fixed or moving), to a radar receiver. Also, the deflection or indication, ion the screen of a cathode ray tube, representing a contact. Face - The front, or viewing surface, of a cathode ray tube. The inner surface of the face is coated with florescent salts which emit light under the impact of a stream of electrons. FTC - Fast Time Constant is a circuit in the radar designed to reduce clutter by reducing part of the echo having a long time duration. Gain (RCVE) - A control used to increase or decrease the sensitivity of the receiver (RCVR) controls the intensity of the received contact echoes. Heading Flash - An illuminated radial line on the face of the radar scope for indicating the ship's heading on the azimuth ring. Intensity - A control for regulating the amount of background light of the radar scope. Interference - Confusing signals or patterns produced on a radar indicator by another radar on the same frequency, and more rarely, by the effects of nearby electrical apparatus or machinery, or by atmospheric phenomena. Megacycle Per Second (MC) - A frequency of one million cycles per second now referred to as MHz (MEHA HERZ) or KHz (KILO HERZ). Microsecond - One millionth of one second. Microwaves - Very short radio waves used in radar usually 3*2 centimeters (CM) or 10 centimeters. Plan Position Indicator (PPl) - A polar presentation centered on the radar antenna. The sweep moves radially from the center of the tube face, and the sweep line rotates in synchronism (scans) with the antenna. Thus the radial distance at which an echo appears is an indication of range, and the angular distance measured clockwise from true north is an indication of bearing. PPI Repeater - Unit which duplicates PPI indication at a location remote from the main radar installation. Presentation - The form which the radar echo signals are made to take on the cathode ray tube screen, as determined by the nature of the sweep circuit utilized. Pulse - A momentary, sharp change in a current or voltage, followed almost immediately thereafter by sharp return to normal. 10-2 Pulse Duration - The elapsed time "between the start and finish of a single pulse. Pulse Length - The time duration of a short burst of the radar signal measured in microseconds. Pulse Repetition Rate (PRE) - The number of pulses transmitted per second. Radar Indicator - A unit of radar equipment which provides a visual indication of the reflected energy received, using a cathode ray tube or tubes for such indication. The radar indicator comprises, besides the cathode ray tube, the sweep and calibration circuit, and associated power supplies. Radar Receiver - An instrument which amplifies radio frequency signals, demodulates the R-F carrier, further amplifies the desired signal and delivers it to the indicator. It differs from the usual radio re- ceiver in that it is more sensitive, has a better signal-noise ratio, and is designed to pass a pulse type of signal. Radar Reflector - A metal device of triangular shape or in the form of three planes mutually perpendicular - analogous to the floor and two side walls in the corner of a room. Used for the purpose of providing a strong radar echo from a known fixed position, such as a seabuoy. Radar Transmitter - A unit of radar equipment in which the radio- frequency power is generated and pulse modulated. Differs from a communications transmitter in frequency and type of modulation used. Radome - A general name for radar turrets which enclose antenna assemblies, usually on airborne installations. Range Markers - Fixed Range Markers are concentric rings of light on 'the face of the radar scope at known ranges. This allows the operator to determine range of a detected contact. Range Selector - Control for selection of range scale on indicator. Refraction - The bending of the radar beam in passing through layers of air of varying density. Resolution - With respect to: (1) Range - The minimum range difference between two separate contacts at the same bearing that will allow both to appear as distinct, separate echoes on the indicator. (2) Bearing - The minimum angular separation between two contacts at the same range that will allow both to appear as distinct, separate echoes on the indicator. (3) Elevation - The minimum angular separation in a vertical plane between two contacts at the same range and bearing that will allow both to appear as distinct separate echoes on the indicator. 10-3 Scan - The area in space covered by moving radar antenna. Scope - The radar scope or cathode ray tube and its control mechanisms. Screen - The large face of the cathode ray tube upon which the contacts are displayed. Sea Return - Clutter about the center of the radar scope which is the result of the radar signal being reflected from the sea, especially near the ship. STC - Sensitivity Time Control is a circuit designed to automatically reduce the sensitivity of the receiver to nearby contacts. Servo - An electro-mechanical system which is used for moving antenna (s) and giving an indication of their position. Sweep - A luminescent straight line formed on the scope face by a moving stream of electrons from within the scope tube. Trigger - A sharp voltage pulse usually of from .1 to .k microseconds, which is applied to the modulator tubes to fire the transmitter, and simultaneously applied to the sweep generator to start the electron beam moving from the sweep origin to the edge of the scope. Variable Range Marker - An illuminated circle of variable diameter that appears on the radar scope. It is placed on the contact in- dicator and the range counter indicates the range in miles and tenths of a mile. 10-4 CHAPTER 10 APPENDIX B - EMERGENCY SHIP HANDLING INFORMATION 05 LT\ EH ^ - v£> a O o - - — oo - - LfA b Jffi JK I H CM o o OJ o L~- oo P o OA D— -3- — — — — CO oj CO LfA VO — ~ OA P p VO LfA LfA O O O 1 O •\ »\ LfA OJ VD OJ »N oo 0O J- VD OJ P OJ LP\ H OJ OJ oo OO OJ OJ LfAVD o OJ H 00-00 OJ OJ VO EH t- a O O ~ E - o OA P K P K i H LfA LfA OJ OJ OA VO o - - o OO — — — — CD o3 H OJ OJ - — O OJ o CO O o ^ O LfA-ch p- 1 O «\ «s, UA o P H • 0J p VD 0O LfA H CO p oo H p H OJ H 0O t>- O P CO O rH H OJ H H-OJ H H 03 VO Eh ^ 00 O _ - E - LfA OA P P P K o O o O VD OO OJ LfA D— o 0O — — — — CO o3 00 LfA p - — o c— p VD o - O O LfA LfA 1 O •\ »s LfA OJ LfA H • OJ OAVO P O 6 a r-i H OJ cd H oo LfA H J- OO 0J -0O OJ OJ CQ 0) 03 t> ON 03 EH _ — VO £ O o - - - o LfA p p p p i on o OJ vb c— oo OJ n E OA LfA H — — — — co . 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Draft 2k' 00" Aft. Draft 6k RPM Ahead 15 Sec. Shaft stop 37 Sec . Shaft going astern 76 RPM Astern 568' Advanced over course 67 Sec. Time dead in water 90° Change in ship heading stbd. Steering engine must respond at a minimum of 2-l/3° per second - minimum requirement of MARAD construction. Most vessels respond at the rate of 50 Sec. from hard right to hard left. 11,150 DWT Vessel - Speed 11 Kts. - 50 Sec. from hard right to hard left. Ship heading change: 25° in k-0 Sec. Vessel swings at the rate of approximately 10° for every 15 Sec. 10-6 FULL AHEAD: HALF AHEAD: SLOW AHEAD: (SUPER TANKER OR SUPER BULK CARRIER) Emergency Stop for 26,500 DWT - 750' Length Draft: 30' Fwt. 33' Aft. 96 RPM - (Ahead) 32 Sec. Shaft stop 1 Min. 37 Sec. Shaft going astern 60 RPM Full astern 4,800' Advanced over course 8 Min. Time dead in water 110° Change in ship heading to stbd Same as (Full Ahead) except one-half speed 65 RPM Ahead 25 Sec. Shaft stop 1 Min. k-0 Sec. Shaft going astern 65 RPM Astern 2,760' Advanced over course 5 Min. 18 Sec. Time dead in water 90° Change in ship heading stbd. Same as (Full Ahead) - Slow speed 42 RPM Ahead 15 Sec. Shaft stop 51 Sec. Shaft going astern 60 RPM Astern 1,020' Advanced over course 2 Min. 50 Sec. Time dead in water 2° Change in ship heading stbd . 10-7 FULL AHEAD: HALF AHEAD: SLOW AHEAD: (Ck - S - B5) FULLY LOADED Draft: 29' Fwd. 31' Aft. 75 RPM (15-8 Kts. ) Shaft stop Shaft going astern 15 Sec. 55 Sec. 78 RPM 3,600' 5 Min. Advanced over course k-0 Sec. Time dead in water 112° Change in ship heading to stbd. Same as (Full Ahead) except at one-half speed 50 RPM (11 kts. ) 10 Sec. Shaft stop k-5 Sec. Shaft going astern 60 RPM Astern 1,050' Advanced over course 2 Min. 50 Sec. Time dead in water 51° Change in ship heading to stbd. Same as (Full Ahead) - Slow Stop 30 RPM 7 Sec. Shaft stop kO Sec . Shaft going astern 68 RPM Astern 360 ' Advanced over course 1 Min. 30 Sec. Time dead in water 8° Change in ship heading to stbd, 10-8 BIBLIOGRAPHY Brown, Ernest B., U. S. Naval Oceanographic Office, "Simplified Radar Plotting", Journal of Institute of Navigation, Washington, D. C, 1969. Burger, W. RADAR OBSERVER'S HANDBOOK FOR MERCHANT NAVY OFFICERS, Glasgow, Brown, Son & Ferguson, 1957* 155 P« illus. Hengst, Christian. PRACTICAL RADAR NAVIGATION. New York: Codan Marine, Inc., c. 1964. 56 p., illus. Institute of Navigation, THE USE OF RADAR AT SEA. Fourth Revised Edition. F. J. Wylie, ed. New York: American Elsevier Publishing Co., 1968. 280 p., illus. Martin Roca, Lorenzo. USO DEL RADAR A BORDO. Publication Especial Num. 9. Cadiz, Instituto Hidrografico De La Marina, 1961. 264 p., illus. Moss, W. D. RADAR WATCRKEEPING. Great Britain: The Maritime Press Limited, 1965 . 968 p., illus. Oliver, Edward F., Cdr., United States Coast Guard, "Rapid Radar Plotting". Maryland: Weems & Plath, Inc., 1969. 6 p., illus. Oudet, L. RADAR AND COLLISION. Princeton, N. J,: Van Nostrand, i960. 89 p., illus. Robb, Ellis M. RADAR PLOTTING. Liverpool: C. Birchall, 1955. 48 p., illus. Slack, Robert M., "The Keystone System of Anti-Collision Radar Navigation" Journal of the Institute of Navigation, vol. ±k, No. 2. Summer 1967* Thayer, Louis M. PRACTICAL RADAR PLOTTING. Portland, Oreg. : Tech. Pub. Service, 1956. 26 p., illus. U. S. Naval Oceanographic Office, AMERICAN PRACTICAL NAVIGATOR, Bowditch. Washington: U. S. Government Printing Office, 1958. U. S. Naval Oceanographic Office, H.O. Pub. No. 257, RADAR PLOTTING MANUAL. Washington, D. C, 1968. Vandegrift, John F. CAPTAIN VAN'S HANDBOOK ON RADAR SAFETY AT SEA. Groves, Tex.: Captain Van's School of Navigation, 1959« 31 p«> illus. 10-9 PENN STATE UNIVERSITY LIBRARIES AD00D71EbS322