2.ecece Locatiox Procedures The location of tne ship was determined with the assistance of four types of equipment. For the most part they represent independent methods. The equipments were: (1) Raydist, an electronic navigation device (3) (4) Alidades combined with a gyrocompass Mk. 18 Taut wire equipment (2) Sextants Tne Raycist principle is that the distance between two points can be measurec by counting the number of standing radio waves between tne two points. More specifically the difference in radius from two shore points is determined by measuring the difference in the number of standing waves. In the actual equipment this is accomplished by measuring the phase of a 4LOO-cycle beat note at three fixed receiving sta- tions. This beat note is produced by transmitters of approximately 12.5 mc, one of which is fixed and the other on the ship being tracked. The Raydist equipment as actually used involved installations requiring 6Q-cycle power at each of four shore points. Each of these shore installations had a transmitter and three of them had receivers in addition. On shipboard the installation, which of course required an additional source of 60-cycle power, was comprised of three receivers, @ transmitter, and equipment for the phase comparison. While Raydist equipment permitted the determination of the ship's position easily to within 20 ft, it had the limitation that the ship's location was determined only relative to some fixed point where the ship must have been. This fact combined with the fact as noted that five sources of 60-cycle power were required (four on shore at isolated locations and one on the ship) proved to be one of the major headaches in the actual operation of the equipment. since if any of the five power supplies failed, it was necessary to repeat *he run and return the ship to the known starting point. The sextants used were standard Navy issue except that they could be read to 10 sec. The general limitations on the use of sextants were found to be very extensive, since three well defined shore points whose location is known are required and the strength of the fix approaches zero as the ship approaches the circle determined by the three shore points. There is the further limitation that if very distant shore points are used, then even the full angular accuracy of the sextants results in relatively poor absolute precision of the Pix. Finally, the capability for finding and retaining ill-defined objects with the sextants was much poorer than with the alidades. For these various reasons, in practice the sextants were used only as a backup procedure for locating the ship and were used only occasionally. A gyrocompass Mk. 18 was installed on the boat for the use of this project, and two repeaters, one on the flying bridge and the other on the forward starboard 40 mm gun mount, were installed. These repeaters were complete with alidades naving a magnification of about 2.5. In practice the alidades and gyrocompass proved to constitute the best method of positioning the snip and this equipment was used either <0 agar