The processing and editing steps on board the ship were:
(A.) Demultiplex, or unravel, the acquired Simrad data files using RT to generate separate files containing navigation, depth soundings, sidescan sonar backscatter values, and sound velocity information.
(B.) Automatically reject bad data (autoRejectSoundings). For the multibeam soundings, reject data outside expected depth ranges (operator's decision based on nautical chart data); for navigation data, reject fixes with poor GPS statistics.
(C.) Edit the navigation data on-screen using jview to remove undesirable points, including turns at the ends of survey lines.
(D.) Edit the multibeam soundings on-screen using swathed to remove individual anomalous soundings.
(F.) Map the bathymetric soundings from each processed data file onto a Mercator grid using weigh_grid with node spacings and scale selected by the operator.
(G.) Map the extracted sidescan sonar backscatter values onto a digital mosaic using mos2 in the Mercator projection at a scale selected by the user.
(H.) Using addSUN, generate bathymetric raster files using the mapped grid node information to depict the depth information in a shaded relief Mercator map. A Mercator projection allows individual map areas to be joined edge to edge when creating a composite image. The shaded relief images were generated using a sun elevation angle of 45 degrees from an azimuth of 0 degrees, and a vertical exaggeration of four times to emphasize sea floor features.
(I.) Generate a false colored image using mix_ci by combining the bathymetric and backscatter raster mosaics into a single image, also in the Mercator projection.
Additional processing in the laboratory included adjusting the bathymetric observations to mean sea level using predictions of the ADCIRC tidal model (see Westerink, J.J., R.A. Luettich, Jr. and J. Muccino, 1994, "Modeling Tides in the Western North Atlantic Using Unstructured Graded Grids", Tellus, 46a(2):178-199.)
All mapped files are in the Mercator projection, having a central longitude of -75 degrees West, a latitude of true scale of 40 degrees north and the horizontal datum is WGS84. The vertical datum is mean sea level, referenced to the ADCIRC model.