6-m resolution gray-scale image of shaded-relief multibeam bathymetry in western Massachusetts Bay map Quadrangle 3 (Q3_SRELIEF.TIF)

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 produce shaded-relief images. The metadata for the grids describes the processing steps applied to the navigation and bathymetric soundings. The following processing steps produced the image of shaded-relief bathymetry:
1. Create a 6-m grid of the bathymetric soundings for Massachusetts Bay using the SwathEd routine weighgrid.
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 12 -lambda 3 gridFile filename.merged
2. 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
3. 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
4. Convert the contrast-stretched shaded relief image from SwathEd format to a tiff file using the netpbm utilities (http://netpbm.sourceforge.net/):
Command line: rawtopgm -headerskip 1024 image_width image_height filename_shade.stretch | pnmtotiff -none - > filename.tif
5. Create an ESRI world file (tfw) for the shaded relief tiff 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 filename_shade.stretch

Image shifted 1/2 grid cell to northwest (using the ArcMap/Data Management Tools/Projections and Transformations/Raster/Shift tool) to correct for an error identified in the SwathEd gridding algorithm in 2007. Correct world file.

Edits to the metadata were made to fix any errors that MP v 2.9.36 flagged. This is necessary to enable the metadata to be successfully harvested for various data catalogs. In some cases, this meant adding text "Information unavailable" or "Information unavailable from original metadata" for those required fields that were left blank. Other minor edits were probably performed (title, publisher, publication place, etc.). Attempted to modify http to https where appropriate. The source information was incomplete and had to be modified to meet the standard. The metadata date (but not the metadata creator) was edited to reflect the date of these changes. The metadata available from a harvester may supersede metadata bundled within a download file. Compare the metadata dates to determine which metadata file is most recent.

Added keywords section with USGS persistent identifier as theme keyword.