E-1 



TECHNICAL ASPECTS 

 Navigational Capabilities 



One of the prime technical objectives of the field pro- 

 gram was to undertake photographic coverage of the seabed at 

 locations sufficiently well determined so that the locations 

 could be re-occupied and observations repeated in the future. 

 The stringent navigational requirements seem justified by 

 the patchiness of many of the sessile benthic communities. 

 The principal tool of the biological survey was our bottom- 

 towed sled whose cameras record a distant field of view approx- 

 imately 5 meters in width along transects that extended from 

 1 to 12 km in length. 



In order to satisfactorily accomplish the objectives of 

 precise navigation, a goal was set to first locate the sur- 

 face vessel in an absolute geodetic reference frame and then 

 to position the on-bottom sled with respect to the surface 

 vessel. For ease of correlation to existing industrial and 

 other national bathymetric surveys of the outer continental 

 shelf we chose the Universal Transverse Mercator coordinate 

 system as the reference frame. A scale of 1:48,000 was adopted 

 for real-time shipboard navigation; Figure E-1 shows a seg- 

 ment of a typical shipboard track. We later enlarged our 

 maps to 1:24,000 for the post-cruise analysis and synthesis. 



Our philosophy of design and assembly was one of a total 

 integrated system consisting of several navigation sensors 

 interfaced to a digital computer with graphics display. For 

 Leg E-2A-79 at Baltimore Canyon and E-2B-79 oro Georges Bank, 



