Composite sidescan-sonar mosaic collected by the National Oceanic and Atmospheric Administration offshore of Massachusetts in the approaches to Boston Harbor near Hull (DH_NOAA_backscatter1m, UTM Zone 19N, GeoTIFF)

For NOAA Hydrographic survey H10993: Launch 1005 acquired multibeam-echosounder data using a hull-mounted RESON SeaBat 8101 multibeam system. All positioning and attitude on Launch 1005 were determined with a TSS POS/MV 320 (version 2) GPS aided inertial navigation system. Launch 1014 acquired multibeam-echosounder data using a hull-mounted RESON SeaBat 8125 multibeam system. For continuous refraction correctors at the transducer, a Digibar Pro was used for the surface sound velocity and all positioning and attitudes on Launch 1014 were determined with a TSS POS/MV 320 (version 3) GPS-aided inertial navigation system. The RESON SeaBat 8101 is a 1.5 deg beam angle system which operates at a frequency of 240 kHz and collects 101 individual soundings in a swath oriented perpendicular to the vessel track. The RESON SeaBat 8125 is a 0.5 deg beam angle system which operates at a frequency of 455 kHz and collects 240 individual soundings in a swath oriented perpendicular to the vessel track. Sounding positional control was determined using the Global Positioning System (GPS) corrected by U.S. Coast Guard differential GPS (DGPS) beacon stations. The primary and only DGPS beacon used for this survey was Portsmouth Harbor, NH (Beacon # 771). No horizontal control stations were established for this survey. NOAA's Computer Aided Resource Information System (CARIS) directory with all of the processed multibeam bathymetric data was provided to the USGS. The raw eXtended Triton Format (XTF) multibeam backscatter data from NOAA survey H10993 was also delivered to the USGS where it was processed using a radiometric-correction technique developed by the Ocean Mapping Group and the University of New Brunswick (Beaudoin and others, 2002). Refer to the Fall Data Acquisition and Processing Report (DAPR) and the Horizontal and Vertical Control Report, for detailed equipment, vessel configuration and setting information. No additional visual enhancement was performed. Significant tonal variation occurs in this dataset as a result of the system parameters during acquisition.