NAVIGATION 



Precision navigation for the deep -tow work was furnished by the FPS-16 Radar 

 Facility of the Pacific Missile Range on die island of Kauai. This facility was unable 

 to furnish assistance during;run number four due to other commitments, therefore 

 navigation for run number four was by means of ship's radar. 



The FPS-16 Radar navigation fixed the position of the ship three times each minute 

 during profile runs. These fixes were tabulated by the FPS-16 computer facility as 

 ranges, bearings, and depression angles to the ship. 



This precision navigation information was not available on the ship during the 

 runs so it was necessary to monitor progress along the run by means of ship's radar. 

 As an additional check on progress along the runs and to make sure the FPS-16 Radar 

 was tracking the correct target, a rough plot was maintained at the Radar Facility. 



The precision of the navigation for the ship provided by the FPS-16 Radar Facility 

 probably exceeds our need for knowing ship's position; however, it is necessary to 

 have a horizontal component of bottom slope for the analysis. In these profiles, the 

 speed of the fish is essentially that of the ship so the precision navigation is assumed 

 to apply to the fish as far as speed over the ground is concerned. In die analysis of 

 the data the horizontal component of the bottom slope is that determined by the pre- 

 cision radar navigation for all runs except number four. The horizontal component 

 for run number four is determined from die ship's radar navigational information. 



GENERAL TOPOGRAPHIC RESULTS 



The most important topographic feature of die reconnaissance area is a scarp 

 which trends from southwest to northeast through the eastern portion of the area. It 

 essentially forms the eastern margin of the range area. 



This scarp is typified by depth changes of the order of 600 to 1000 feet and slopes 

 in excess of 35 degrees and possibly as much as 60 degrees. 



Figure 4 shows the three east -west profiles which cross the scarp. The topog- 

 raphy east of and above the scarp is relatively featureless and smooth with bottom 

 slopes of 2 to 4 degrees. Below the scarp in these profiles the depth increases ima 

 gently undulatory fashion from about 550 fathoms at the base of the scarp to approxi- 

 mately 1000 fathoms toward the western end of the profiles. 



Note that the bottom slopes are moderately steep in the western portions of the 

 profiles. It is this steepness which first suggested the value of a slope analysis and 

 its application to the bottom bounce sonar bearing error problem. 



SLOPE ANALYSES 



The data for the slope analyses came from profiles 4, 5, 6 and 7. Profiles 4, 6 

 and 7 are east -west trending and profile 5 is north -south trending. The records for 

 each of these runs were read at 200 -yard intervals of horizontal distance and the tan- 



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