Interpretation of the distribution of anthropogenic deposits on the inner-continental shelf within the New York Bight, derived from geophysical data collected by the U.S. Geological Survey, 1995 - 1999 (Esri polygon shapefile, Geographic, WGS84)

DGPS is assumed to be accurate within 1-2 meters. Standard GPS is assumed accurate within 5-10 meters. 99% of the positional data is DGPS. Unless noted, all GPS/DGPS data is referenced to WGS84 (NAD83). Slant-range distance is recorded between the sidescan-sonar tow vehicle and a sidemount rigged with an acoustic transponder. Offset between the sidemount and GPS antennae is measured. Basic trigonomic calculations use the slant-range offset to calculate a 'fish' (tow-vehicle) navigation. An assumption in these calculations is that the tow-vehicle is traveling directly behind the vessel; movement to port or starboard is not accounted for within 'fish' navigation. Thus, the horizontal accuarcy of the sidescan-sonar tow-vehicle is +/- 15 meters. The horizontal positioning of the seismic systesm did not account for source and receiver offsets and offset the GPS antennae and the boomer source and streamer. It is estimated that these offsets could lead to inaccuracies of about 30 m.
Interpretive products are based on the evaluation of sidescan-sonar, seismic-reflection, and sample data. Therefore, the horizontal accuracies of these systems will carry through to the interpretive products. As such, the horizontal accuracy of these data is assumed to be within +/- 30 meters.