More information about the individual USGS surveys conducted as part of the Buzzards Bay project can be found on WHCS Field Activity Web pages:
2009-002-FA: <http://woodshole.er.usgs.gov/operations/ia/public_ds_info.php?fa=2009-002-FA> 2010-004-FA: <http://woodshole.er.usgs.gov/operations/ia/public_ds_info.php?fa=2010-004-FA> 2011-004-FA: <http://woodshole.er.usgs.gov/operations/ia/public_ds_info.php?fa=2011-004-FA>
Information about the NOAA survey can be found at:
H11319: <http://surveys.ngdc.noaa.gov/mgg/NOS/coast/H10001-H12000/H11319/DR/>
This shapefile includes trackline navigation from all the swath bathymetric data that was collected within the survey area. However, only quality sonar data along the main survey lines were included in the final bathymetry grid that is found on this report (BB_Bathy5m). Noisy or poor quality data were not included in the grid. Data from some survey lines were omitted where they overlapped with equal or better quality data from adjacent lines (as was the case for the few lines that were less than several hundred meters long). Data along tie and transit lines were not included in the final grid. Also, data from the southern extent of line l131f1 were omitted as they extended beyond the survey area boundary into an area covered by a previous NOAA survey (see NOAA Survey H11076 <ftp://ftp.ngdc.noaa.gov/pub/coast/H10001-H12000/H11076/> and USGS Open File Report 2006-1357 <http://pubs.usgs.gov/of/2006/1357/>).
Field activities 2009-002-FA and 2010-004-FA: Navigation was acquired with a Coda Octopus F180 Differential Global Positioning System + Wide Area Augmentation System (DGPS+WAAS); which are accurate to + or - 1 to 2 meters, horizontally. All DGPS data are referenced to WGS84. The SWATHPlus transducers were mounted on a rigid pole, approximately 2.46 m below the water line, along the starboard side of the M/V Megan T. Miller. The DGPS antenna was located on the same pole approximately 4.3m above the sea surface. These offsets were corrected within the SWATHPlus acquisition software.
Field activity 2011-004-FA: Navigation was acquired with a Coda Octopus F180 Differential Global Positioning System + Wide Area Augmentation System (DGPS+WAAS); which are accurate to + or - 1 to 2 meters, horizontally. All DGPS data are referenced to WGS84. The SWATHPlus transducers were mounted on a rigid pole, approximately 2.17 m below the water line, along the port side of the M/V Scarlett Isabella. The DGPS antenna was located on the same pole approximately 4.6m above the sea surface. These offsets were corrected within the SWATHPlus acquisition software.
The DGPS horizontal positional accuracy is estimated to be within 3-5 m; WAAS enable DGPS accuracy is estimated to be within less than 3 m and the accuracy of RTK-GPS (which was not applied to the horizontal positions for these surveys) is estimated to be less than 1 m. However, the U.S. Coast Guard maintains a maritime DGPS service providing 10 meter accuracy for the coastal areas of the continental US; therefore, a very conservative, worse-case estimate of the horizontal positional accuracy of this survey data is approximately 10 meters (although these systems have been shown to be reliable to less than 2m). (sources: <http://www.noaa.gov>; <http://www.nos.noaa.gov>; <http://www.ngs.noaa.gov>; <http://www.nstb.tc.faa.gov/>; <http://www.navcen.uscg.gov>).
USGS Configuration: Survey: Survey lines were run at an average speed of 5 knots and were spaced 50-100 m apart to obtain overlapping swaths of data and full seafloor coverage. Sonar: The SEA SWATHplus-M operates at a frequency of 234 kHz and a variable range (increased or decreased manually depending on water depth). The system was operated with a transmit power: 80 percent, a transmit length: 12 cycles (2009-002-FA and 2010-004-FA) or 43 cycles (2011-004-FA), 3072 samples per channel (2009-002-FA) or 4096 samples per channel (2010-004-FA and 2011-004-FA), and a variable range (increased or decreased depending on water depth).
Additonal sonar configuration information can be found in the metadata for the bathymetry grid included with this report (USGS Open-File Report 2012-1002, High-Resolution Geophysical Data from the Inner Continental Shelf: Buzzards Bay, Massachusetts at <http://pubs.usgs.gov/of/2012/1002/html/appendix1.html>)
NOAA Configuration: Survey: All data were collected by the NOAA Ship RUDE. Trackline spacing for survey H11319 was based on an estimate of 2.5 times the water depth to achieve overlapping swaths for full seafloor coverage. For this area survey lines were typically between 25-50m apart. Ship speed was determined such that the survey achieved a sampling rate of 3.2 pings per 3 meters of along track distance. Sonar: The RESON SeaBat 8125 is a 0.5 degree (across-track) by 1 degree (along-track) 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. The system is capable of ping rates ranging from 3.02 Hz to 40.05 Hz but for this survey, the maximum ping rate was set to 20 Hz. Other: All bathymetry processing, including navigation editing, was done by NOAA Hydrographers. NOAA's Computer Aided Resource Information System (CARIS) directory was provided to the USGS. 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.
Additonal sonar configuration information can be found in the metadata for the bathymetry grid included with this report (USGS Open-File Report 2012-1002, High-Resolution Geophysical Data from the Inner Continental Shelf: Buzzards Bay, Massachusetts at <http://pubs.usgs.gov/of/2012/1002/html/appendix1.html>)