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 (UNB), Canada,
was used to process and grid the multibeam bathymetric soundings and backscatter intensity data, and to produce images. The metadata for the grids describes the processing steps applied to the navigation and bathymetric soundings. The following processing steps produced the shaded relief image of bathymetry, colored by backscatter intensity:
1. Create backscatter files that can be then mosaicked from the backscatter time series:
Command line: getBeamPattern filename (prefix only)
Command line: makess -pixel 3.0 -beam_patt beampatt filename (prefix only) output.ss
Command line: glfill output.ss output.ss_fill (fills in data dropouts).
2. Mosaic all the backscatter files created in the last step (for each output.ss_fill), and then use a two point linear contrast stretch to enhance the backscatter image.
Command line: mos2 -autoseam -maxazi 10 -maxdist 10 mosaic_file output.ss_fill
Command line: stretchacres -low 180 -high 220 -in mosaic_file -out mosaic_file.stretch
3. Create a shaded relief image of the bathymetry using SwathEd routine addSUN (sun elevation of 45 degrees from 350, vertically exaggerating 4 times).
Command line: addSUN -elev 45 -azi350 -vert_exag 4.0 gridFile.r4 filename.shade
4. Use a two point linear contrast stretch to enhance the shaded relief image:
Command line: stretchacres -low 150 -high 200 -in filename.shade -out filename_shade.stretch
5. Create an image of shaded-relief topography, colored by backscatter intensity:
Command line: mix_ci -c mosaic_file.stretch -i filename_shade.stretch -m mosaic_file.pseudo
6. Create a tiff from the psuedocolored backscatter mosaic file using the netpbm utilities (
http://netpbm.sourceforge.net/):
Command line: rawtopgm -headerskip 1024 image_width image_height mosaic_file.pseudo | pnmtotiff -none - > mosaic_pseudo.tif
7. Create an ESRI world file (tfw) for the pseudocolored backscatter intensity image for import to ArcView or ArcGIS. Copy bounding box and resolution information from the jview program output to the .tfw file.
Command line: jview mosaic_file.pseudo