Man has been navigating for many centuries. It would seem that there would be little room left for improving his methods, yet he has been able to determine his longitude at sea for only a little more than two hundred years, and the line of position from a celestial observation has been known scarcely a hundred years. Twenty years ago many aviators were navigating with road maps. Ten years ago the first crude radar was being tested.
Navigation is becoming ever more expansive. When Nathaniel Bowditch published the first edition of the American Practical Navigator in 1802, he was able to provide in one volume all the information that was necessary to navigate a ship on any ocean. Included in this book was instruction in mathematics, navigation, meteorology, and oceanography. In addition, it provided almanac information and tables for dead reckoning, piloting, and celestial navigation. Today whole libraries are devoted to the subject, and more than two dozen agencies in the Navy Department alone are directly concerned with navigational problems. The need for a central co-ordinating office is recognized by some of the agencies concerned.
Navigation has progressed more during the last 25 years than during any previous century. Until World War II, developments followed each other slowly enough to permit the average officer to gain at least a speaking knowledge of new things as they came along, but during the war one development followed another so closely that few of us realized how fast we were traveling along the road of progress. Since the shooting has stopped, we have had a chance to catch our breath and cast a quick look back to see how far we have traveled.
Increase in Interest
Evidence of the increased interest in navigation in recent years is the organization of the Institute of Navigation in 1945, the formation of the International Civil Aviation Organization (ICAO) and the International Meeting on Marine Radio Aids to Navigation (IMMRAN) in London in 1946 and in the United States in 1947.
Various colleges have recently added courses in navigation and even high schools have become interested in the subject. The British have established an Empire Air Navigation School to insure adequate training for their air navigators. Canada has instituted a somewhat similar program. One interesting feature of these courses is their goodwill training flights to distant parts of the earth.
Before being retired from service, the British Lancaster bomber Aries became known in many parts of the world by its visits as part of this program. Data collected on its arctic flights over both magnetic and geographical poles in 1945 contributed to the adoption of a new position for the former about 300 miles northward and a little west of its previously accepted position on Boothia Peninsula. The collection of such data is not outside’ the province of such a flight, for the Empire Air Navigation School is the center for air navigational research in Great Britain.
There is no counterpart of this school in the United States, but an American naval officer has suggested that a four-year college- level course be established to produce navigational engineers who would be well versed in the many varied aspects of the expanding science of navigation.
Among the many navigational developments of the last few years, no more striking progress has been made than in the field of electronics.
Electronic Navigation
Before World War II, electronic navigation consisted essentially of the use of the radio direction finder, the radio ranges and beacons of the airways, radio time signals, and communication. During recent years many electronic aids have been developed or proposed.
Radar
The atomic bomb may have been the most spectacular scientific development of the recent war, but radar undoubtedly contributed more than any single development to our success. Like most great scientific developments, radar did not emerge fully grown overnight. As early as 1886, long before the advent of the commercial broadcasting station, it was proven that radio waves are reflected from solid objects. In 1904 a German engineer was granted a patent in several countries on a proposed method of using this principle as an obstacle detector and a navigational aid for ships.
In 1922 scientists testing plane-to-ground communications at the Naval Aircraft Radio Laboratory in Anacostia noticed that ships moving in nearby Potomac River distorted the pattern of radio waves, causing a fluctuating signal. Recognizing the importance of this discovery, scientists began to explore its possibilities, but progress was slow until 1935, when Congress appropriated $100,000 to the Naval Research Laboratory for the specific development of radar. A rather crude radar was tested successfully aboard the U.S.S. Leary in 1937 and a greatly improved one was given extensive sea trials aboard the U.S.S. New York in 1939. Before that, experimental work conducted ashore employed a variety of ships and aircraft and the dirigible Akron.
Let it not be inferred from what has been said that radar was developed solely by the United States Navy. The idea that the pulse technique could be used to detect and range objects such as aircraft and ships seems to have occurred independently and almost simultaneously in the United States, England, France, Germany, and perhaps also in Japan. Scientists in these countries worked secretly on various practical aspects of the problem.
Probably no scientific development in the history of the world has expanded on such a scale in all phases simultaneously. Research, development, production design, production, field trials, and training of thousands of operators and technicians had to go on at the same time, not to mention the education of commanding officers to the capabilities of this new instrument and the development of new doctrine based upon its use. This was not aided by the cloak of secrecy which had to be maintained if the full advantage to this development was to be realized.
The basic principle of radar is simple. A short, powerful burst or pulse of electromagnetic energy is transmitted and the time required for it to travel to an object and part of the energy to be reflected back is measured in microseconds (millionths of a second). The information is displayed by means of a cathode ray tube, the two most frequently used forms being the A scope, on which a horizontal trace serves as a time base for measurement of time between two vertical elevations called pips; and the PP1 scope, a chart-like presentation of the surrounding area.
Radar is used for navigation in a variety of ways. If bearings of two or more objects are observed, a fix can be plotted as if the bearings were obtained by visual observation. Bearing is determined by noting the direction in which the directional antenna is pointed, but the width of the beam results in slight uncertainty. For this reason a fix determined by plotting circles of position using two or more ranges is generally more accurate. If only one object is available, both bearing and range can be used to obtain a fix.
To facilitate the use of radar for navigation, various beacons and reflectors have been developed. The racon, developed for aircraft use, consists essentially of a transponder, a receiver-transmitter which receives a radar pulse and transmits a coded signal. Positive identification of a charted position is thus provided and the useful range of radar is extended because the returning signal is much stronger than a reflected echo. Both bearing and range information can be obtained as with reflected signals.
A different type radar beacon, called a ramark, has been developed by the Coast Guard for marine use. It produces a narrow ray of light on the PPI scope at the bearing of the beacon, even when the ramark is well beyond the maximum range for which the PPI is set. Since the ramark is not beyond the experimental stage, very few are in existence. These or an improved type of radar beacon will undoubtedly be available generally along the coasts of the United States within a few years.
A simple reflector attached to an existing aid to navigation, such as a buoy, to provide stronger signals on the shipborne radar, has demonstrated its value, but is also not yet generally installed.
The development of the PPI scope has provided a unique method of determining position not available in other aids. The scope picture can be compared with a chart of the area, and the ship’s position determined by matching the two presentations. To facilitate this use of radar, special charts were developed during the war. These were first made aboard ship, but later this function was transferred to the Hydrographic Office. Drawn to the same scale as the PPI, the chart was designed to be used with a Virtual PPI Reflectoscope (VPR), a device attached to the front of a radar to produce a virtual image at the face of the PPI scope.
Templates made from scope photographs have been used, and the Army Engineers have experimented with mosaic charts made from progressive scope photographs as a vessel moved along the channel of the Ohio River.
The Coast and Geodetic Survey has printed a regular navigational chart showing land contours in a manner which might be useful to the radar equipped ship. It has been suggested that the usefulness of such contours would be increased if they were labeled in distance to the horizon, rather than height above sea level. A more promising suggestion is that the contours be replaced by PPI mosaics overprinted as a tint.
Various radar charts for use by aviators have been published, principally by the U. S. Air Force Aeronautical Chart Service.
Experiments have been conducted to determine the suitability of using shore-based radar for harbor supervision. Notable among these is the work done at Liverpool, where the principal dock area is reached only after negotiating some 14 or 15 miles of narrow channel. A properly placed radar can provide surveillance for the entire channel and be of inestimable assistance to ships entering or leaving the port during thick weather. It is anticipated that the use of this radar will be to provide guidance, rather than control. The installation is also useful for checking the navigational aids in the harbor to see if any is out of position.
While experiments go forward to determine the most effective method of using radar for navigation, present installations continue to be of tremendous assistance to the navigator. In common with other aids, however, radar is no cure-all, and must be used with judgment and skill. Its greatest limitation is its range. Because it is limited approximately to line-of-sight distance, it is essentially a piloting aid. Its greatest navigational value is in providing a method of using piloting techniques in virtually any weather.
Hyperbolic Systems
Several electronic systems have been developed to provide position fixing information over greater range than is possible with radar. The best known of these is loran, one of several systems providing hyperbolic lines of position.
A series of loran lines of position are provided by two ground transmitters spaced about 200 to 400 miles apart. The short, pulsed signals from these stations are carefully synchronized, the difference in transmission time being known within an accuracy of two microseconds. A special receiver- indicator is used to measure accurately the difference in the time of arrival of the signals from the two stations. All craft having the same reading are thus a constant difference in distance between the two transmitters, or along a hyperbola. Each time difference reading thus defines a hyperbolic line of position. Certain controlled delays are introduced between the signals of the two transmitters forming one pair, or rate, to prevent the readings from repeating on each side of the center line midway between the two transmitters, and for other reasons.
Two such lines of position establish a fix. Special charts or tables are needed to translate the readings to geographical co-ordinates. Time difference readings can be obtained rapidly in virtually any weather, after very little training. Plotting time is comparable to that required for celestial lines of position.
By means of loran, piloting technique is extended some 600 miles to sea by day and 1,400 miles by night, when sky waves are reflected from the ionosphere. Over most of the coverage area a fix determined by ground or direct waves is comparable in accuracy to a good fix obtained by celestial observation aboard ship. A sky wave fix is comparable to a good celestial fix in the air.
Two methods of extending the range of loran without increasing the number of stations have been proposed. One of these is to increase the power and the other is to use a lower frequency. Both will probably be used. Standard loran operates at a frequency only slightly above the commercial broadcast band used in the United States. Low frequency loran has been tested rather extensively. The chief obstacle encountered involves the identification of ground and sky waves, for, at the frequency used, the pulses are so long that the direct and reflecting signals merge and cannot be separated as in standard loran.
Loran is easy to use and operators can be trained in a few days. It does not require transmission from the ship or aircraft, but it does necessitate the maintenance by the government of expensive shore stations, some of which might be vulnerable in time of war. Thus, we might be denied the use of those in advance areas at the time they are most needed. If but a single loran line of position can be obtained, it can be used with a line determined by any other method.
Single lines are often convenient for use in homing. The indicator is set to the reading of a line passing through the destination and the craft steered to keep the reading constant. During World War II aircraft leaving the Marianas to bomb Tokyo found this use of loran very convenient.
Of the various systems requiring shore transmission, loran is one of the most attractive from a frequency economy standpoint, since as many as 16 pairs of station or “rates” can transmit on the same frequency by varying the repetition rate of the signals.
Loran is much newer than radar. Its development was more rapid because much of the information learned in perfecting the pulse technique of radar was useful in loran, and also because a loran receiver is a simple instrument compared to a radar set.
Work on loran was commenced in 1941 at the Radiation Laboratory of the Massachusetts Institute of Technology, and during the winter of 1942-1943 the North Atlantic chain of transmitting stations was placed in operation. Coverage was available in the Alaska area a few months later, closely followed by installation of stations in the Hawaiian Islands, many islands in the Western Pacific, and as far west as India. The last coverage provided was on the West Coast of North America.
During the war loran, like radar, was a closely guarded secret.
The most recent developments in loran have been the adding of speedometer type counters to simplify reading, and the building of a receiver that permits essentially simultaneous readings of two rates.
Even before the development of loran the British were working on a similar system called gee. It differs principally from loran in using frequencies of 20 to 85 megacycles, resulting in much shorter range, and also in a pulse recurrence rate about ten times that of loran. Each pair of gee stations operates on a different frequency. Gee receivers are built so as to permit readings of two pairs of stations simultaneously. Several gee stations are in operation in or near the British Isles.
Another recent British development is the hyperbolic system known as Decca. In this system each master station operates with two or three “slaves,” each transmitting on a separate frequency. The stations broadcast continuous waves, rather than pulses, and the distance difference is determined by measuring the phase relationship of the signals arriving at the receiver.
The readings from all “rates” of a set are continuously and automatically indicated, appearing on three dials. The system is extremely simple to use and provides position lines which are much more accurate than those of either loran or gee. The usable range, however, is limited to about 250 or possibly 300 miles.
The principal disadvantage of Decca is that its coverage area is divided into a number of lanes. The same reading can be obtained in any lane. A ship or aircraft leaving a known position has no trouble identifying its lane, unless temporary interruption of service or power failure causes the receiver to get out of step. However, lanes are so narrow that a craft entering any given Decca pattern is often uncertain of its correct lane. A method of lane identification has been devised but its effectiveness is yet to be proved.
Several Decca stations have been installed in the vicinity of the British Isles.
Other Electronic Aids
During the war the Germans developed an interesting radio beacon they called Sonne. Since the war the British have improved the system and named it Consol. To make a reading it is necessary only to count a series of dots and dashes and refer to a special chart, scale, or table. The resulting line of position is a great circle originating at the transmitter. Although the system is easy to use, it has not yet been demonstrated to be more accurate than an average ship’s dead reckoning position. Its effective range is probably not more than a few hundred miles.
Two Consol stations have already been placed in full-time operation in northern Europe, and two more in part-time operation in Spain.
All of the electronic aids discussed thus far are available to both ships and aircraft. Several systems have been devised to replace the radio range beacons marking the airways of the United States, which have several serious limitations, chief of which are that each beacon provides only four on- course signals and makes no provision for parallel courses to handle a large flow of traffic.
An ommi-directional beacon developed by the Civil Aeronautics Administration overcomes the four-course limitation of the older system, which may be discontinued after installation of the new beacons has been completed. To use the ommi-directional beacon, an aircraft must have a special receiver which has a left-right dial indicating continuously whether the aircraft is off its pre-selected course, and to which side. With the addition of distance measuring equipment (DME), a continuous fix will be available to aircraft. If an automatic computer is added, courses to off-set points become available, thus providing parallel courses along an airway.
Other recent electronic advancements include the development of high frequency direction finders and automatic direction finders for use in aircraft. The latter provide continuous indication of the direction of the transmitter by means of a pointer and a dial.
Low Visibility Landing Systems
One of the principal problems of military or commercial aircraft operation is the provision for landing planes during periods of low visibility. Two electronic methods of doing this are being used.
The Army and Navy use a system called Ground Controlled Approach (GCA), in which special radar operators on the ground “talk down” the incoming aircraft, giving the pilot verbal information as to his position relative to his glide slope.
Civilian airports use GCA to some extent, but generally favor a system of beams and beacons called Instrument Landing System (ILS).
Another approach to the problem has been the attempt to disperse fog over the airport. To date the most successful method of removing fog has been to burn it off by means of a series of burners lining the runway. Gasoline is the fuel most frequently used, but kerosene, fuel oil, and diesel oil have been used successfully. This system, called Fog, Intensive Dispersal of (FIDO) has been used to remove fog near the ground to a sufficient height to permit landing by GCA or ILS, but in its present form it is much too expensive for general use. Fog has also been removed by the use of sound and chemical drying agents. Experiments in fog removal are being conducted at the Navy’s Landing Aids Experimental Station, at Areata, California, the country’s foggiest airport.
Traffic Control
Control of air traffic in congested areas is not strictly a navigational problem, but is closely related. Many traffic control systems have been proposed, but none has received wide approval. Most methods involve the use of radar in some form, and at least one includes the use of television.
Celestial Navigation
Developments in celestial navigation, while overshadowed by advances in electronics aids, have not been lacking. In 1935, Hydrographic Office publications No. 208 (Dreisonstok) and 211 (Ageton) were still the “last word” in navigation. The principal advance since then has been the appearance of various tabulated solutions which have rendered trigonometric solutions obsolescent.
The first volume of H.O. 214 appeared in 1936. The set was not completed until Vol. IX was published ten years later. The printing of H.O. 218 paralleled that of H.O. 214.
The latest addition to this type of celestial table, H.O. 249, was published in June, 1947. In a single volume about the size of one volume of H.O. 214, this book tabulates the altitude and azimuth (not azimuth angle, 0° to 180°) of six selected stars for each full degree of the local hour angle of Aries (LHAT). Thus, if a watch regulated and set to sidereal time is used, no almanac is needed. Because of the precession of the equinoxes, this volume must be recomputed or a correction provided every few years. The Hydrographic Office is considering the publication of accompanying declination tables for use with the sun, moon, and planets since H.O. 249 proved so popular.
Some American navigators have suggested the preparation of destination tables. The Japanese published such tables as supplements to their almanac. In these tables the altitude and azimuth of certain bodies are tabulated against time for specified locations. By using these locations as assumed positions and comparing the tabulated altitudes with observed altitudes, the navigator is able to obtain lines of position very quickly.
The American Air Almanac, now used universally by American aviators and by many marine navigators, began with the January-April issue of 1941. Since its appearance there has been almost continuous agitation for revision of the Nautical Almanac. A new design patterned somewhat after the Air Almanac is available for 1950. Samples pages were issued in 1948 and the entire almanac has now been printed.
The bulky Rude Star Finder which was popular for many years has given way to the handy, compact, round H.O. 2102-C, now generally used for locating stars.
One of the more interesting developments of World War II was the application of night vision technique to celestial observation. Developed to increase the effectiveness of lookouts during darkness, this technique consists of dark-adapting the eyes by the wearing of red glass goggles for 25 to 30 minutes and then directing the sight some distance above or below, or to one side, of the point to be viewed, so that it is observed out of the “corner” of the eye, the most efficient part when there is little light.
Several submarine navigators claim reasonably accurate fixes from observations made by marine sextant during the night.
Instruments
Marine sextants have remained essentially unchanged since they were first invented independently by Godfrey in 1730 and Hadley in 1731. The two principal improvements were the early addition of a telescope and the recent substitution of a micrometer drum for the difficult-reading vernier. Many small changes in aircraft bubble sextants have resulted in instruments much superior to those in use at the start of the war. Many other instruments have also been improved during recent years. Notable among these is the development of remote reading magnetic compasses for both aircraft and ships, and the greatly improved standard magnetic compasses for use aboard ship.
An instrument to provide an automatic dead reckoning position, the dead reckoning tracer (DRT), has long been available for ships. An aircraft version was developed during World War II. Instruments to provide a continuous position by celestial mean? may not be as far away as some believe.
Polar Navigation
Since the end of hostilities, considerable attention has been given to polar navigation. While expeditions entered polar regions many times prior to World War II, interest in these areas was confined to a small group of explorers. Since the war polar operations have been almost continuous. While navigation in the vicinity of the poles is basically no different from that anywhere else, the application of basic principles is in some cases unique.
It is necessary for the polar navigator to re-orient himself and acquire the “polar concept.” Such familiar terms as direction, latitude and longitude, time, day and night, sunrise and sunset all take on different meanings.
On polar charts meridians radiate outward from the pole like spokes of a wheel, and parallels appear as circles. True direction changes so rapidly that two persons within sight cannot be considered to be on reciprocal bearings. Each might be north (or south) of the other if the pole is between them. Because true direction is of little value near the pole, it is seldom used. Aircraft attempt to travel a great circle (not a series of rhumb lines approximating a great circle). This has resulted in the development of the grid system of navigation, in which actual meridians are discarded in favor of fictitious ones. On the chart these appear much the same as the meridians of a Mercator chart near the equator. Following a fictitious rhumb line making the same angle with all fictitious meridians is no more difficult than following an actual rhumb line in low latitudes. Both approximate a great circle. Variation with respect to the grid meridians can be shown on charts more easily than variation with respect to true meridians, since lines of equal grid variation do not converge at the geographic pole, as do the familiar isogonals. Grid navigation, proposed during the . war by Wing Commander Kenneth C. Mac- lure, of the Royal Canadian Air Force, is now used extensively in polar regions. The principal exception is the plotting of lines of position from celestial observations, which is often done by means of actual meridians and parallels, which are also shown on the charts.
The horizontal intensity of the earth’s magnetic field is weak in most parts of both polar regions, and marine gyro compasses become less effective as the pole is approached. This has led to the development of an electric directional gyro compass with very little precession. It is checked at intervals by means of an astro compass. The principal difficulty in maintaining direction is the dependence on celestial bodies for such checks. At the pole the sun is above the horizon six months and below it for an equal period. Twilight lasts for several days, during which time direction cannot be maintained for a sustained flight by present equipment. A sky compass being developed is expected to provide observations during this blind period.
Before the last war polar charts were almost non-existent. Today charts of the polar regions are available on a variety of projections—stereographic, inverse Mercator, gnomonic, azimuthal equidistant, and a recent adaptation of the Lambert conformal. These charts, however, are inadequate because of the absence of accurate surveys of these regions. The lack of charts of the accustomed accuracy is understandable when the inaccessibility of these regions is considered.
The Hydrographic Office has recently published an Ice Atlas of the northern hemisphere which has proved to be accurate and very helpful in arctic regions.
Because of the interest in polar regions, the navigation of land vehicles has received increased attention. Improved instruments are being developed for this purpose.
Charts
Charts are available in such numbers and with such accuracy that the average navigator is likely to take them for granted, being quite unaware of the long process of development that has produced such dependability.
With the impetus of war, chart producing facilities were greatly expanded. Most of the Pacific theater was without modern charts at the start of the war, but surveying parties followed close on the heels of landing forces. Faster chart producing methods were developed and placed aboard ships operating in advanced areas, so that little time elapsed between the surveys and delivery of completed charts.
Besides the usual navigational charts, special charts were made for electronic aids such as radar and loran, a handful of aeronautical charts were expanded to include world-wide coverage on several scales and projections, and many special charts were made, such as waterproof pilot charts printed on silk for use in lifeboats. Since the war a new series of magnetic charts has been published.
One of the principal problems of the geodesists has been the measurement of long distances over open water or inaccessible terrain. Several new developments help extend the measurable range, the two most significant being shoran and the flare method.
Shoran consists essentially of a radar-type transmitter and two land-based transponder- type beacons. Both returning signals are picked up by a special receiver which indicates distance from the beacons. Developed during the war to permit precision bombing during periods of low visibility, shoran has since been used by the surveyor with remarkable success, distances of several hundred miles having been measured with an error of only a few yards.
The visual range has also been extended by means of the “flare method.” A plane drops a flare at a considerable height over the inaccessible area. The bearing is meassured at two or preferably three stations whose positions are accurately known, thus locating the position of the flare. The process is repeated once or twice with flares at different places. The bearing of each flare is also observed at the station whose position is sought, which is thereby located with reference to the flares, and hence with reference to other stations of known position.
Meteorology
Meteorology has not escaped without significant development. Among the improved methods of obtaining information has been the use of radar to detect the presence and location of precipitation. Planes are now sent out to track tropical storms, so that adequate warnings can be broadcast to vessels and aircraft. The use of dry ice to precipitate snowfall from super-cooled clouds has been tested. Thirteen weather ships are being stationed in the Atlantic to constitute a weather network to provide more reliable weather data for this area. Several land stations have been established in the arctic.
Perhaps the most interesting meteorological advance was the development by Dr. John C. Bellamy, a meteorologist formerly at the University of Chicago, of basic formulas for determination of drift correction angle by comparison of absolute and barometric altimeters at intervals. This has led, also, to the development of pressure pattern and single heading flying, two variations of a method of reducing flight time over a long over-water distance such as the North Atlantic by choosing a route that results in favorable winds, even though it may be considerably longer than the great circle route. Radio station WSY at New York broadcasts weather information essential to the effective use of these methods.
Oceanography
Until World War II the navigator’s chief interest in the work of the oceanographer concerned tidal predictions and ocean currents. But in the recent conflict his services were sought to predict surf conditions at prospective beach-heads and in supplying information on underwater sound conditions, which proved of inestimable value to submarines and anti-submarine vessels alike.
The most spectacular oceanographic development was the discovery of an underwater sound channel at a considerable depth below the surface. A small depth charge exploded at about 4,000 feet below the surface near Dakar, Africa, was heard 3,100 miles away in the Bahama Islands.
This discovery is being put to use by the installation of two listening stations on the West Coast and one in the Hawaiian Islands. The Bureau of Ordnance has developed a depth charge to be carried by lifeboats and life rafts. This depth charge will explode when it reaches the proper level, and time of arrival of the sound will be measured to an accuracy of a tenth of a second at the three listening stations. The difference in the time of arrival at the various stations will define hyperbolic lines of position similar to those of loran. It is expected that the position of the lifeboat can thus be located within an elliptical area about a mile and a half wide and four miles long.
A Division of Oceanography has recently been established at the Hydrographic Office to serve as a center for the oceanographic work of the government.
Training
The impact of World War II necessitated such tremendously rapid expansion of training activity that advanced techniques had to be developed if the program was to be successful. Perhaps the most significant advance in this field was the development of various synthetic training devices, such as the Link celestial trainer, radar ultrasonic trainer, and the loran supersonic trainer. A Special Devices Center was created by the Navy to develop and produce a long list of training aids. Numerous movies, produced principally by the Navy, were made available to assist in the training program.
Present Needs
With all of these advances in navigation, the ultimate has not yet been reached. There are a number of improvements needed, some urgently. Among them are the following:
(1) The most promising electronic aids should be selected and expanded on a worldwide basis. There are so many conflicting systems being proposed that confusion results and proper development and expansion are hindered. Energies are being scattered throughout the world. A unification-of effort, properly channelled, could provide much needed global coverage in a relatively short time.
(2) If the maximum benefit is to be gained from the systems selected, adequate training of operating personnel must be provided.
(3) An adequate traffic control system for high density air traffic is urgently needed.
(4) The most effective type of chart for use with radar should be determined.
(5) A better aircraft sextant is needed, particularly one that will reduce the observation time below the two-minute period common with present instruments.
(6) Better refraction tables, particularly for low altitudes, are needed, primarily for use in polar regions where the only bodies visible are often near the horizon.
(7) If celestial navigation is to maintain a place in the air, it will eventually have to become essentially automatic, probably without its present weather limitations. That is, practically continuous positions must be available in any weather.
(8) A polar navigation manual is needed for training the large number of navigators being sent into polar regions without an adequate appreciation of the problems to be encountered and the available knowledge of .how to solve them.
(9) More accurate polar charts are urgently needed.
(10) More accurate magnetic charts are needed, particularly in polar regions.
(11) Additional weather reporting stations are desirable, especially in polar regions to permit more adequate forecasting coverage.
(12) The required equipment of every lifeboat should include a simple navigation kit consisting of waterproof pilot charts, an inexpensive sextant, almanac information, tables for solving celestial observations, information on identification of stars, adequate plotting equipment, and a brief discussion of lifeboat navigation, with particular attention to instructions for use of the equipment supplied. Such a kit can be small and inexpensive.
(13) As aircraft speeds reach and pass the sonic barrier, an entire new set of instruments, including those used for navigational purposes, may be needed.
(14) If guided missiles are to have the great range predicted, a method of navigating them must be found.
Conclusion
Development in navigation has been rapid during the last few years, because requirements have advanced. That further progress is essential is indicated by the needs listed above. Answers to these needs will be found, thus creating additional requirements. Such is the nature of progress.
When push-button navigation becomes a reality, the need for a navigator will not be ended. The navigator of tomorrow will be more highly skilled, better trained, and more alert than the best of our present navigators, for he will have to understand and interpret information from a variety of intricate instruments unknown to us today. He will have to know when an instrument is giving inaccurate information. The speeds at which the air navigator will travel will necessitate almost instantaneous decisions. He may well be the senior member of the crew.
Let us have such development, by all means, and let us use it to the fullest possible extent. But let us remember, also, that the most perfect instrument that can be invented is subject to mechanical failure. Let us remember, too, that lifeboats and life rafts still serve more than an aesthetic purpose. Of necessity war-trained navigators were taught only the essentials for their anticipated service. Let it not be inferred that because they did a creditable job, such training is adequate. The prudent navigator will continue to learn and practice basic navigational methods, so that he will be prepared for any reasonable emergency, and not place all of his navigational eggs in one fragile, mechanical basket.