Data collected for the mapping cooperative have been released in a series of USGS Open-File Reports<http://woodshole.er.usgs.gov/project-pages/coastal_mass/html/current_map.html>. This spatial dataset is from the Cape Ann and Salisbury Beach Massachusetts project area. They were collected in two separate surveys in 2004 and 2005 and cover approximately 325 square kilometers of the inner continental shelf. High resolution bathymetry and backscatter intensity were collected in 2004 and 2005. Seismic profile data, sediment samples and bottom photography were also collected in 2005.
The positional accuracy of the final georeferenced Klein backscatter mosaic was adjusted by registering the Klein mosaic to the backscatter collected with the SEA SwathPlus bathymetric sonar. The SwathPlus backscatter has better positional accuracy because the GPS antenna was mounted directly over the sonar head to minimize xy offsets between the acquired RTK-GPS position and SwathPlus sonar transducers.
The specific parameters used in Xsonar are listed below:
Demultiplexing Range and Filter Option: Swath Width= 200m Across Track/Along Track Filter= 4 x 3 pings Port and Starboard Normalize=4000 pings Input= 16 bit
Beam Patter Correction: Number of lines= 150 Ping Overlap=75 Max Beam Angle=90 Response Angle:55
dd if=filename.ras of=filename.ras bs=80 skip=1
These resulting rasters (.ras) were converted to a TIFF using Adobe Photoshop (ver. 10).