in conjunction with Raydist or taut wire in nearly all runs. ~ The taut wire equipment consisted of a drum about 20 in. in diameter wnicn could be controlled by a hand-operated brake, together with a@ pulley and counter for measuring the amount of wire reeled out anda balance complete with fish scale for measuring wire tension. This equipment was felt to be the most reliable of all the procedures for locating the ship and was used on all surveys. It proved, however, to have some important limitations. For one thing, the wire did not run freely and tended to go into oscillation if the boat's speed was too high. In fact, this upper limit on the boat's speed was very close to the lower limit which was required for proper steering of the boat. Occasional runs were encountered in which analysis indicated that the anchor nad not remained fixed. 2.3 TEST PROCEDURES AND DISCUSSION 2.3.1 Preshot Surveys Preshot surveys were made to the extent possible in the circunstances of each shot. For Shot 1 the only preshot survey possible was to determine the water depths on the lagoon side of the reef. As was expected, only a very small sector of the area which was ultimately within the crater could be reached by the survey boat before the shot. This survey was performed using all of the aids t> boat location, and served as a very useful comparison and trial of the various methods. The preshot survey of the Snot 4 location permitted a much more extensive survey since the shot point was in navigable water. A complete and fairly detailed bottom survey was accomplished for roughly 2 square miles of bottom in the area of the shot point. In this area primary dependence was placed on tne Raydist equipment for location of the boat since shore points were ilistant and hard to see. The presnot survey of Shot 3 was comprised of contours run on Tare Island by the H&N surveyors sombined with a bottom survey made by the project group using botn Raydist and shore fixes. Since the shot yield was smaller than expected and tne crater was almost landlocked, the only significant preshot survey was made by the H&N surveyors. in addition to the surveys by which elevation and position were determined, aerial photographs were taken of each shot point for use in comparison with postshot photographs. Such photographs were taken of all shot points regardless of whether a bottom survey at the shot was contemp ated. 2.3.2 Postshot Surveys The post-Shot 1 survey was made using all four location aids listed under section 2.2.2. Since very few shore points could be identified and tney were poorly located for surveying purposes, a series of three buoys was placed in a line on tne lagoon side of the crater to serve as sextant aids. The buoys proved to be useless because they could not be seen for the requirei distance under the light conditions which existed.