A suite of processing software (called SwathEd) (www.omg.unb.ca/~jhc/SwathEd.html), developed by the Ocean Mapping Group at the University of New Brunswick, Canada, was used to process and grid the multibeam bathymetric soundings and backscatter intensity data, and to produce images. The metadata for the bathymetry grid (see link in larger work citation) describes the processing steps applied to the navigation and bathymetric soundings. The following processing steps produced the shaded-relief image for the Moriches data set:
1. Create a 3-m grid of the bathymetric soundings for the Moriches site using the SwathEd routine weigh_grid.
Command line: weigh_grid -fresh_start -omg -tide -coeffs -mindep -2 -maxdep -800 -beam_mask -beam_weight -custom_weight EM1000_Weights -butter -power 2 -cutoff 6 -lambda 1.5 gridFile filename.merged
2. Create a shaded-relief image of the bathymetry using SwathEd routine addSUN (sun elevation of 45 degrees from 60, vertically exaggerating 4 times). The shaded relief file created from the grid is mapped into the same projection as the grid and carries over the projection information (custom Mercator projection, central meridian -75 degrees, latitude of true scale 40 degrees north) used to create the grid.
Command line: addSUN -elev 45 -azi 60 -vert_exag 4.0 gridFile.r4 filename.shade
3. Use a two-point linear contrast stretch (0-254; 255 is no data) to enhance the shaded-relief image:
Command line: stretchacres -low 150 -high 200 -in filename.shade -out filename_shade.stretch
Note: An error in the UNB processing software that incorrectly projected the multibeam observations onto a plane was discovered in 2003. These data were processed with corrected software.