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/>
The Klein 3000 was towed from the stern A-frame of the M/V Megan T. Miller. Real-Time Kinematic (RTK) GPS position data were provided by the NovAtel DL-V3 receiver and recorded to the raw data files (XTF) via SonarPro (version 11.0) on the sonar acquisition computer. The GPS antenna was mounted on the top of the SWATHplus (interferometric bathymetry) transducer pole, midship on the starboard side (the middle of the 3 bathymetry system antennas). On a few brief occasions the RTK-GPS signal was lost and the navigation system fell back to standalone DGPS or GPS mode. In these cases, the lower quality positions were used and no corrections were made for RTK navigation gaps. All GPS data during this survey were referenced to the WGS84 horizontal datum. The horizontal offsets between the GPS antenna and the sheave on the A-frame were measured prior to the survey (x: -4.1m; y: -14.94m; z: -1.33m). The side-scan tow cable was deployed through a 3PS digital block cable counter attached to the A-frame. Real-time cable-out measurements were transmitted via serial connection to the SonarPro acquisition software, which calculated tow-fish layback. All horizontal offsets were applied in the acquisition software so the navigation recorded in the XTF data reflect the position including the layback offset. The layback calculations do not account for fish motion behind the vessel, which is caused by sea state and vessel speed induced changes in the angle and scope of the tow cable. RTK positional accuracy is estimated to be less than 1 m. Taking the additional fish motion, cable movement and RTK-GPS navigation dropouts into account, as well as the mosaicking process, the positional accuracy for this dataset is estimated to be within 30 m.
Field activity 2011-004: The Klein 3000 was towed from the stern A-frame of the M/V Scarlett Isabella. Differential GPS (DGPS) position data were provided by the Ashtech BRG2 receiver and recorded to the raw data files (XTF) via SonarPro (version 11.0) on the sonar acquisition computer. The GPS antenna was mounted on the forward end of the acquisition lab van. All GPS data during this survey was referenced to the WGS84 horizontal datum. The horizontal offsets between the GPS antenna and the sheave on the A-frame were measured prior to the survey (x: +4.31m; y: -9.18m; z: 0.0m). The side-scan tow cable was deployed through a 3PS digital block cable counter attached to the A-frame. Real-time cable-out measurements were transmitted via serial connection to the SonarPro acquisition software, which calculated tow-fish layback. All horizontal offsets were applied in the acquisition software so the navigation recorded in the XTF data reflect the position including the layback offset. The layback calculations do not account for fish motion behind the vessel, which is caused by sea state and vessel speed induced changes in the angle and scope of the tow cable. DGPS positional accuracy is estimated to be within 3-5 m; WAAS enable DGPS is estimated to be less than 3 m. Taking the additional fish motion and cable movement into account, as well as the mosaicking process, the positional accuracy for this dataset is estimated to be within 30 m.
2009-002-FA SonarPro version: 10.0 nav: from the antenna on the aft end of the acquisition van into the Ashtech BRG2 receiver (DGPS) sheave offsets x: -2.0m; y:-8.35m; z:+2.0m
2010-004-FA SonarPro version 11.0 nav: from the center antenna on the SWATHplus pole into the NovAtel DL-V3 receiver (RTK) sheave offsets x:-4.1m; y:-14.94m; z:-1.33m
2011-004-FA SonarPro version 11.0 nav: from the antenna on the fwd end of the acquisition van into the Ashtech BRG2 receiver (DGPS) sheave offsets x: +4.31m; y:-9.18m; z:0.0m
Below are the typical parameters for processing with XSonar: File Type: XTF, Low Frequency (132 kHz)
Setup Option: Navigation= Lat/Lon Navigation Interval= 1 minute
Demultiplexing Range and Filter options: Across track=4 (pixels) Along track= 3 (pixels) Port/Starboard Normalize = 4095 (default) Port High Pass: 65535 (default) Input= 16 bit Normalize Image= yes.
Beam Pattern Correction options: Number of lines= 90 Ping overlap=45 Max beam angle= 90 (default) Response angle=55 (default) Data normalization (0-255)=1 (default) Port/Stbd Tone Adjustment= "on" and "Normal"