II. SURVEY OPERATIONS 

 A. Conduct of Survey 



The area surveyed was subdivided into three separate rectangles 

 totaling about 30,000 square miles. This was done in order to cover 

 all the known seamounts in the time available for the survey oper- 

 ations (Fig. 1). Survey lines in Areas A and C were run normal 

 to the axial trend of the seamount chain at a spacing of five nautical 

 miles. In Area B, lines were run at the same spacing, but in a North- 

 South direction. The average ship's speed when surveying was 12 knots, 

 Bathymetric and magnetic data were collected simultaneously along all 

 survey lines. 



Throughout the survey area, the ship's position was determined 

 by Loran-A, and the fix time-interval was normally 15 minutes. Be- 

 tween the time of sunrise and sunset, fix accuracy was about + 2 

 miles. Tracks run at night generally were dead-reckoned when Loran-A 

 reception deteriorated because of local weather and sky-wave con- 

 ditions. Strong westerly ocean currents in Area A and the western 

 part of Area C made it difficult for SHELDRAKE to maintain the intended 

 courses. 



The survey of the seamount chain was accomplished in three phases 

 of approximately two weeks each. Data were collected on four of five 

 enroute tracks between New York and the survey area. Data also were 

 obtained on the final track which terminated in Norfolk, Virginia. 

 The tracks were spaced to make best possible use of the ship's survey 

 capabilities (Fig. 1). 



