10-m resolution image of shaded relief multibeam bathymetry in Massachusetts Bay (MB_SRELIEF10M.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 10-m grid of the bathymetric sounds for Massachusetts Bay 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 20 -lambda 5 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 each 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

Reprocessing to correct projection error An error in the UNB processing software that resulted in the multibeam observations not being properly projected onto a plane was discovered in 2003. These software errors were corrected and the data re-gridded. The shaded-relief images presented here in the Stellwagen Bank region may differ from preliminary versions included in the following publications: Butman, B., and Lindsay, J.A. (Eds.), 1999, A marine GIS Library for Massachusetts Bay: focusing on Disposal sites, Contaminated Sediments, and Sea Floor Mapping: U.S. Geological Survey Open-File Report 99-439, 1 CD-ROM. (Also available on line at http://pubs.usgs.gov/of/of99-439/start.htm) Gutierrez, B.T., Butman, Bradford, and Blackwood, D.S., 2001, Photographs of the sea floor of western Massachusetts Bay, offshore of Boston, Massachusetts, July 1999: U.S. Geological Survey Open-File Report 00-427, 1 CD-ROM. (Also available on line at http://pubs.usgs.gov/of/of00-427/) Valentine, P.C., Middleton, T., and Fuller, S., 2001, Maps showing sea floor topography, sun-illuminated sea floor topography, and backscatter intensity of the Stellwagen Bank National Marine Sanctuary region off Boston, Massachusetts: USGS Open-File Report #00-410, 1 CD-ROM, scale 1:60,000. (Also available on line at http://pubs.usgs.gov/of/of00-410/)

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 2.9.30 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.). 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.