The geophysical mapping utilized a suite of high-resolution instrumentation to map the surficial sediment distribution, depth and sub-surface geology: dual-frequency 100/500 KHz sidescan-sonar system, 234-KHz interferometric sonar, and 500 Hz -12 KHz chirp sub-bottom profiler. The survey was conducted aboard the M/V Megan Miller August 9-13, 2007. The study area covers 35 square kilometers from about 0.2 km to 5-km offshore of the south shore of Martha's Vineyard, and ranges in depth from ~ 5 to 20 meters.
Data files were recorded by SEA software SWATHplus 3.05.19 in the SWATHplus SXR format. Data collection parameters are saved into a SWATHplus session file in SEA's SXS format that can be later used for data replay.
Pitch, roll, heading, and heave information were recorded using a Coda Octopus F180R motion reference unit (MRU) (see: <http://www.codaoctopus.com/motion/f180/index.asp>) and transmitted via network connection to the SWATHplus data collection software. The MRU sensor was mounted directly above the SWATHplus transducers, thereby minimizing "lever arm" offsets which can lead to positioning and depth errors in the bathymetric data. The F180R series MRU uses two L1 antennas for position and heading accuracy. These were mounted directly above the MRU with an offset of 6.76 meters. The antennas are mounted on a rigid horizontal pole with a separation of 1 meter and are offset from the MRU in a forward/aft configuration. The forward offset of the primary antenna from the MRU is 0.5 meters, with no port/starboard offset.
Sound Velocity Profiles (SVP): Fourteen sound velocity casts were collected at various intervals during the USGS cruise 07011 using an Applied Microsystems SV Plus v2 instrument (see <http://www.appliedmicrosystems.com/products/productDetails.aspx?id=1> for details). Sound velocity profiles (SVP) were generally collected at the eastern and western ends of the survey area, corresponding to the start and/or end of geophysical line data collection. This procedure was primarily followed to coordinate collection of SVP casts with the beginning or end of trackline. This was acceptable because only small variations in the speed of sound were noted throughout the survey area and negligible refraction artifacts were visible within the swath bathymetric data.
Primary navigation antenna to MRU: Height offset: -6.76 meters Forward offset: 0 meters Starboard offset: 0 meters
Draft of the MRU below water line: 2.6 meters.
Offset of SWATHplus transducer 1 (port side) from the CRP: Height offset: 0.158 meters Forward offset: -0.019 meters Starboard offset: -0.11 meters
Offset of SWATHplus transducer 2 (starboard side) from the CRP: Height offset: 0.158 meters Forward offset: -0.019 meters Starboard offset: 0.11 meters
Software: SWATHplus 3.05.19
Software: SWATHplus 3.05.19
Software: SWATHplus 3.05.19
Low amp: 100 Range: Max amplitude 4 meters, min amplitude 0 meters Quality: 0.8 Box: Min depth 3 meters, max depth 30 meters, min horizontal range 0 meters, max horizontal range 25 - 50 meters (increasing with trackline spacing). Along track 1: Max depth difference 10 meters, window size 10, learn rate 0.6 Along track 2: Max depth difference 0.5 meters, window size 2, learn rate 0.8 Mean output processed pixel size: 1meter.
Software: SWATHplus 3.05.19
Software: SWATHplus 3.05.19
Software: Grid Processor 3.02.19
Software: SWATHplus 3.05.19
Software: CARIS HIPS/SIPS 6.1
East: 366027 West: 373547 North: 4578733 South: 4573363
Software: CARIS HIPS/SIPS 6.1
Software: CARIS HIPS/SIPS 6.1
Software: CARIS HIPS/SIPS 6.1
Software: IVS DMagic 6.7.0
Only the highest resolution DTM surface ( 2-m resolution ) was exported from IVS Data Magician as an ArcView Grid (ESRI ASCII grid) .
Software: IVS DMagic 6.7.0
The projection of the grids was then defined as UTM, zone 19N, WGS84, using Arc Toolbox, Data Management Tools, Projections and Transformations, Define Projection.
Software: ESRI ArcGIS 9.2
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