5-meter contours produced from bathymetric data collected by the U.S. Geological Survey off the southern shore of Martha's Vineyard, MA, 2007 (ESRI POLYLINE SHAPEFILE, CON_5M)

Swath bathymetric data were collected using an SEA Ltd SWATHplus 234-kHz Interferometric Bathymetric Sonar (<http://www.sea.co.uk/swathplus.aspx?nav=products> ) during survey operations. The SWATHplus system was mounted as a sidemount and positioned on the starboard side of the R/V Megan Miller. Line spacing varied from 40 meter in ~ 5 to 15 meter water depth to 70 meters in ~15 - 25 meter water depth. 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.

Offsets of the SWATHplus transducers and DGPS navigation antenna from the F180R motion reference unit (MRU), which is the designated common reference point (CRP), were verified as entered correctly into the SWATHplus session file for the survey. Offsets forward, below, and to the right (starboard) of the CRP are considered positive: 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

Water level heights for the duration of the survey were incorporated into the SWATHplus session file. The Woods Hole Oceanographic Institution Martha's Vineyard Coastal Observatory (MVCO) maintains an instrumented node at a depth of 12 meters that records a variety of oceanographic data including water level heights above the node (<http://www.whoi.edu/mvco/description/description2.html>). Oscillation of the water level above the node is recorded in a file that was downloaded and parsed for these heights (OcnDat_s, see: <http://www.whoi.edu/mvco/data/oceandata.html>). These heights are referenced to a vertical datum of 11.68 meters, which represents a long term mean depth directly above the node (August 2006 - present). These data are not tied into any chart datum (i.e. Mean Lower Low Water). The data were reformatted for input into the SWATHplus session file and stored in the file 2007_JD221-225_tides_swathplus.dat. We chose to use these water level heights because other oceanographic data from the 12 meter node will be used in conjunction with the bathymetric grid for oceanographic modeling. Software: SWATHplus 3.05.19

Data from the sound velocity profiles were incorporated into the SWATHplus session file. The velocity data is stored in Microsoft Office Excel 2003 SP3 csv format, and the location and time, as well as the velocity information, were extracted from the csv file and entered into the sound velocity profile dialog in SWATHplus. One Julian day's worth of sound velocity data was entered into SWATHplus; the program is limited to a total of 5 velocity profiles at a time. Software: SWATHplus 3.05.19

Various filters were set in the SWATHplus software in order to refine the depth of the seafloor across the swath for each ping based on the phase and amplitude of the returning sonar signal. Only the filters listed below were set, all others were turned off. Filter settings: 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

Patch test lines were replayed through the SWATHplus software after the tides, velocity profiles (for that day), and filters were set and saved in the SWATHplus session file. Processed data files were saved in the SWATHplus sxp format. Software: SWATHplus 3.05.19

The patch test processed sxp files (patch1 - patch7.sxp) were imported into the SWATHplus Grid Processor program and run 3 times through the calibration tool to determine any static offsets for roll. Results: Port roll offset = +0.64 degrees, Stbd roll offset = -0.91 degrees. These offsets were then entered into the SWATHplus session file. Software: Grid Processor 3.02.19

Raw SXR bathymetry data were replayed line by line through the SEA SWATHplus software to produce final processed SWATHplus sxp files. Velocity profiles were incorporated into the session file five at a time bracketing (in time) the bathymetric data collected for that line. This ensures that during the time the bathymetry data were collected, sound velocity information closest in time were utilized by the SWATHplus program to correct for variations in sound velocity through the water column, minimizing ray bending effects that can produce erroneous depth soundings. The SWATHplus software applies the pitch, roll, heave, and heading data supplied by the F180R MRU, ensuring that the depth solutions across the swath are compensated for any motion of the SWATHplus transducers due to ship motion. Software: SWATHplus 3.05.19

All the processed SWATHplus sxp files were imported into CARIS HIPS/SIPS software (www.caris.com) using the CARIS HIPS Conversion Wizard. The selected raw data type was SWATHplus. The conversion wizard converts the depths, navigation, and motion data recorded in the sxp files into an internal CARIS HIPS format. Software: CARIS HIPS/SIPS 6.1

Using the SWATHplus sxp survey lines that were imported into CARIS, a field sheet and BASE surface were generated in CARIS HIPS that encompassed the field area. The field sheet is in the UTM projection, 19N, central meridian -69.0 degrees west. The horizontal datum was chosen to be the WGS 84 ellipsoid. The extent of the field sheet is (in UTM meters): East: 366027 West: 373547 North: 4578733 South: 4573363
Software: CARIS HIPS/SIPS 6.1

A Bathymetry Associated with Statistical Error (BASE) Surface was generated from the survey line data using the bounds from the field sheet properties. A BASE surface is a georeferenced image of a multi-attributed, weighted-mean surface. A BASE Surface can also contain a visual representation of horizontal and vertical uncertainty. A BASE Surface file is saved with a HNS extension (HIPS Navigation Surface). An XML file with the same name as the BASE Surface is also generated when the Surface is created. This file contains the metadata for the Surface. Base surfaces were generated at a resolution of 10, 5, and 2 meters, and the surface type was set to swath angle. The maximum footprint size in the BASE surface that a sounding was utilized was set to 9 pixels, and the include status for soundings were set to accepted, examined, and outstanding. Additional attributes were set for the surface: Density, mean, and standard deviation. Software: CARIS HIPS/SIPS 6.1

Each of the BASE surfaces was interpolated in CARIS HIPS. The interpolation is only applied to areas of no data, and helped to fill in small gaps in the surface. Parameters used for the interpolation were: Matrix size 5X5 pixels, minimum number of neighboring pixels required for interpolation was 6. Software: CARIS HIPS/SIPS 6.1

The final interpolated base surfaces generated in CARIS HIPS was imported into IVS3D's Data Magician (DMagic), a program that is part of the IVS3D Fledermaus suite (www.ivs3d.com). The data magician directly imports the CARIS HNS file described above, and creates a DTM (digital terrain model) and associated geo file for each surface. Software: IVS DMagic 6.7.0

The DTM surfaces created in the Fledermaus Data Magician (DMagic) were converted to a Fledermaus sd file that can be used in the Fledermaus program for three dimensional visualization of the DTM. 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 ESRI ASCII grids were then imported to ArcGIS 9.2 using the ASCII to Raster Tool within ArcToolbox - Conversion Tools - To Raster and output data type defined as float. 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

ArcGIS 9.2 Spatial Analyst extension was used to generate 5-meter contours from the ESRI binary bathymetric grid, bathy_2m. The resulting shapefile has the same projection as the grid (UTM, Zone 19N, WGS84) In order to smooth the resulting contours, an analysis cell size of 50 meters was chosen (Spatial Analyst, Options, Cell Size). High frequency undulations were still present in the contour data. To minimize this "chatter" the Smooth Line tool within ArcToolbox Generalization was used with a smoothing tolerance of 50 meters. The polyline shapefile was then reprojected in Geographic Coordinate System, WGS84, using the ArcToolbox Projections and Transformations, Feature, Project tool.

Edits to the metadata were made to fix any errors that MP v 2.9.36 flagged. This is necessary to enable the metadata to be successfully harvested for various data catalogs. In some cases, this meant adding text "Information unavailable" or "Information unavailable from original metadata" for those required fields that were left blank. Other minor edits were probably performed (title, publisher, publication place, etc.). Reordered the links in the identification section so a landing page link is first. Attempted to modify http to https where appropriate. Moved the minimal source information provided to make it the first process step. The distribution format name was modified in an attempt to be more consistent with other metadata files of the same data format. The metadata date (but not the metadata creator) was edited to reflect the date of these changes. The metadata available from a harvester may supersede metadata bundled within a download file. Compare the metadata dates to determine which metadata file is most recent.

Added keywords section with USGS persistent identifier as theme keyword.