in conjunction with Raydist or taut wire in nearly all runs. The taut wire equipment consisted of a drum about 20 in. in diameter which could be controlled by a hand-operated brake, together with @ pulley and counter for measuring the amount of wire reeled out and a balance complete with fish scale for measuring wire tension. This e- quipment 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 hat fe: Some important limitations. For one thing, the wire did not run fr iy 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 dimit which was required for proper steering of the boat. Occasional: runs were encountered in which analysis indicated that the anchor had not remained fixed. 2.3 TEST PROCEDURES AND DISCUSSION 2.3.1 Preshot: Surveys Preshot surveys were made to the extent possible in the circum- stances 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: gurvey boat before the shot. This survey was performed using all of the aids. to boat location, and served as a very useful comparison and trial of:“the various methods. The preshot survey of.the. Shot 4 location permitted a much more extensive survey since the shot.‘point was in navigable water. A com- plete and fairly detailed bottom survey wag accomplished for roughly 2 square miles of bottom in ‘the area‘of the shot point. In this area primary dependence was placed on he |Raydist equipment for location of the boat since shore points were dist and bard to see. The preshot survey of Shot 3 comprised of contours run on Tare Island by the HAN surveyors combined with a bottom survey made by the project group using both Raydist and shore fixes. Since the shot yield was smaller than expected and the 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 ofeach shot point for use in comparison with postshot photographs. Such photographs were taken of all shot points regardless of whether a bottom eurvey at the shot was contemplated. il cd 2 2.3.2 Postshot Surveys The post-Shot 1 survey was made using all four tocAtion aids listed under section 2.2.2. Since very few shore points could: be iden- tified and they were poorly located for surveying purposes, ai series of three buoys was placed in a line on the lagoon side of the crater to serve as sextant aids. The buoys proved to be useless because they could not be seen for the required distance under the light conditicas which existed. 21