Bathymetric data, stored as elevations relative to IGLD85, collected by the U.S. Geological Survey within the St. Clair River between Michigan and Ontario, Canada, 2008 (ESRI GRID, BATHY_05M)

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Frequently anticipated questions:

What does this data set describe?

Title:
Bathymetric data, stored as elevations relative to IGLD85, collected by the U.S. Geological Survey within the St. Clair River between Michigan and Ontario, Canada, 2008 (ESRI GRID, BATHY_05M)
Abstract:
In 2008, the U.S. Geological Survey (USGS), Woods Hole Coastal and Marine Science Center (WHCMSC), in cooperation with the U.S. Army Corps of Engineers conducted a geophysical and sampling survey of the riverbed of the Upper St. Clair River between Port Huron, MI, and Sarnia, Ontario, Canada. The objectives were to define the Quaternary geologic framework of the St. Clair River to evaluate the relationship between morphologic change of the riverbed and underlying stratigraphy. This report presents the geophysical and sample data collected from the St. Clair River, May 29-June 6, 2008 as part of the International Upper Great Lakes Study, a 5-year project funded by the International Joint Commission of the United States and Canada to examine whether physical changes in the St. Clair River are affecting water levels within the upper Great Lakes, to assess regulation plans for outflows from Lake Superior, and to examine the potential effect of climate change on the Great Lakes water levels ( http://www.iugls.org). This document makes available the data that were used in a separate report, U.S. Geological Survey Open-File Report 2009-1137, which detailed the interpretations of the Quaternary geologic framework of the region. This report includes a description of the suite of high-resolution acoustic and sediment-sampling systems that were used to map the morphology, surficial sediment distribution, and underlying geology of the Upper St. Clair River during USGS field activity 2008-016-FA . Video and photographs of the riverbed were also collected and are included in this data release. Future analyses will be focused on substrate erosion and its effects on river-channel morphology and geometry. Ultimately, the International Upper Great Lakes Study will attempt to determine where physical changes in the St. Clair River affect water flow and, subsequently, water levels in the Upper Great Lakes.
  1. How might this data set be cited?
    U.S. Geological Survey, 2010, Bathymetric data, stored as elevations relative to IGLD85, collected by the U.S. Geological Survey within the St. Clair River between Michigan and Ontario, Canada, 2008 (ESRI GRID, BATHY_05M): Open-File Report 2010-1035, U.S. Geological Survey, Coastal and Marine Geology Program, Woods Hole Coastal and Marine Science Center, Woods Hole, MA.

    Online Links:

    This is part of the following larger work.

    Denny, Jane F., Foster, David S., Worley, Charles R., and Irwin, Barry J., 2010, Geophysical data collected from the St. Clair River between Michigan and Ontario, Canada, 2008-016-FA: Open-File Report 2010-1035, U.S. Geological Survey, Reston, VA.

    Online Links:

  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -82.429028
    East_Bounding_Coordinate: -82.400587
    North_Bounding_Coordinate: 43.015839
    South_Bounding_Coordinate: 42.955703
  3. What does it look like?
    https://pubs.usgs.gov/of/2010/1035/gis_catalog/bathymetry/bathy_05m/bathy_05m_sm.jpg (JPEG)
    Thumbnail image of the color-coded swath bathymetry
  4. Does the data set describe conditions during a particular time period?
    Beginning_Date: 29-May-2008
    Ending_Date: 01-Jun-2008
    Currentness_Reference:
    ground condition
  5. What is the general form of this data set?
    Geospatial_Data_Presentation_Form: raster digital data
  6. How does the data set represent geographic features?
    1. How are geographic features stored in the data set?
      This is a Raster data set. It contains the following raster data types:
      • Dimensions 13285 x 4415 x 1, type Grid Cell
    2. What coordinate system is used to represent geographic features?
      Grid_Coordinate_System_Name: Universal Transverse Mercator
      Universal_Transverse_Mercator:
      UTM_Zone_Number: 17
      Transverse_Mercator:
      Scale_Factor_at_Central_Meridian: 0.999600
      Longitude_of_Central_Meridian: -81.000000
      Latitude_of_Projection_Origin: 0.000000
      False_Easting: 500000.000000
      False_Northing: 0.000000
      Planar coordinates are encoded using row and column
      Abscissae (x-coordinates) are specified to the nearest 0.500021
      Ordinates (y-coordinates) are specified to the nearest 0.500021
      Planar coordinates are specified in meters
      The horizontal datum used is D_WGS_1984.
      The ellipsoid used is WGS_1984.
      The semi-major axis of the ellipsoid used is 6378137.000000.
      The flattening of the ellipsoid used is 1/298.257224.
      Vertical_Coordinate_System_Definition:
      Altitude_System_Definition:
      Altitude_Datum_Name: International Great Lakes Datum (IGLD) 1985
      Altitude_Resolution: 0.5
      Altitude_Distance_Units: meters
      Altitude_Encoding_Method:
      Explicit elevation coordinate included with horizontal coordinates
  7. How does the data set describe geographic features?

Who produced the data set?

  1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)
    • U.S. Geological Survey
  2. Who also contributed to the data set?
  3. To whom should users address questions about the data?
    Jane F. Denny
    U.S. Geological Survey
    Geologist
    384 Woods Hole Road
    Woods Hole, MA
    USA

    508-548-8700 x2311 (voice)
    508-457-2310 (FAX)
    jdenny@usgs.gov

Why was the data set created?

This grid represents approximately 100 kilometers of swath bathymetric data collected within the Upper St. Clair River, May 29 - June 4, 2008. These data are used to define the morphology of the riverbed.

How was the data set created?

  1. From what previous works were the data drawn?
    Information unavailable from original metadata (source 1 of 1)
    U.S. Geological Survey, unknown, Information unavailable from original metadata.

    Type_of_Source_Media: disc
    Source_Contribution:
    Swath-bathymetric and acoustic-backscatter data were acquired with a SEA, Ltd., SWATHplus interferometric sonar operating at a 234-kHz frequency (http://www.sea.co.uk/swathplus.aspx?nav=products). The SWATHplus transducer was mounted at the bow of the USGS R/V Rafael. Bathymetric data were acquired over variable swath widths ranging from 10 to 100 m, in water depths of about 1 to 25 m. A total of 109 km of swath bathymetric data were collected.
    SWATHplus acquisition software (version 3.05.90) was used to digitally log the bathymetric data at a rate of 30 pings/second and 3,072 samples per swath (ping) in the SWATHplus SXR format. Data collection parameters are saved into a SWATHplus session file in SEA's SXS format. These files can be later used for data replay.
    An Octopus F180R Attitude and Positioning system (see: <http://www.codaoctopus.com/motion/f180/index.asp>) recorded ship motion (heave, pitch, roll, and yaw). These data were transmitted via network connection to the SWATHplus data collection software. The Octopus F180R Inertial Measurement Unit (IMU) was mounted directly above the SWATHplus transducers, to minimize lever arm offsets that can lead to positioning errors. The F180R uses two L1 antennas for position and heading accuracy. The antennas are mounted on a rigid horizontal pole, 3 meters above the F180R IMU, with a horizontal separation of 1 meter and are offset from the IMU in a forward/aft configuration. The forward offset of the primary antenna from the IMU is 0.5 meters, with no port/starboard offset.
    Eight sound-velocity profiles were acquired during survey operations at roughly 4-hr intervals using an Applied Microsystems SV Plus V2 Velocimeter (Applied Microsystems, 2008).
  2. How were the data generated, processed, and modified?
    Date: 2009 (process 1 of 15)
    SWATHplus Configuration
    Offsets of the SWATHplus transducers and DGPS navigation antenna from the Octopus F180R Attitude and Positioning System Inertial Measurement Unit (IMU), 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 IMU: Height offset: -3 meters, Forward offset: 0 meters, Starboard offset: 0 meters
    Draft of the MRU below water line: 0.63 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 3.05.19.0 Person who carried out this activity:
    Jane Denny
    U.S. Geological Survey
    Geologist
    384 Woods Hole Road
    Woods Hole, MA
    USA

    508-548-8700 x 2311 (voice)
    508-457-2310 (FAX)
    jdenny@usgs.gov
    Date: 2009 (process 2 of 15)
    Sound Velocity Profiles
    Data from eight sound velocity profiles were incorporated into the SWATHplus session file. The velocity data is stored in Microsoft Office Excel 2003 SP3 commas-separated values (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. Sound velocity information closest in time to the bathymetric data collected are 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.
    Software: SWATHplus 3.05.19.0 Person who carried out this activity:
    Jane Denny
    U.S. Geological Survey
    Geologist
    384 Woods Hole Road
    Woods Hole, MA

    (508) 548-8700x2311 (voice)
    508-457-2310 (FAX)
    jdenny@usgs.gov
    Date: 2009 (process 3 of 15)
    Bathymetric Filters
    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 1 meter, min amplitude 0 meters; Phase Confidence: 70 percent; Angle Proximity: 25 sample window, range 0.11, threshold 9 samples, Minimum elevation -120 degrees; Box: Minimum Depth 0 meters, Minimum Horizontal Range 1 meter; Median sample window size 5; Along track 1: Max depth difference 10 meters, window size 5, learn rate 0.6 Along track 2: Max depth difference 5 meters, window size 1, learn rate 0.9; Mean output processed pixel size: 0.2 meters.
    Software: SWATHplus 3.05.19.0 Person who carried out this activity:
    Jane Denny
    U.S. Geological Survey
    Geologist
    384 Woods Hole Road
    Woods Hole, MA

    (508) 548-8700x2311 (voice)
    508-457-2310 (FAX)
    jdenny@usgs.gov
    Date: 2009 (process 4 of 15)
    Patch Test
    Patch test, used to asses roll offset, lines were replayed through the SWATHplus software after the 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.
    The patch test processed sxp files (p1 through p8.sxp) were imported into the SWATHplus Grid Processor program and run 2 times through the calibration tool to determine any static offsets for roll. Results: Port roll offset = +0.254 degrees, Stbd roll offset = -1.037 degrees. These offsets were then entered into the SWATHplus session file.
    Software: SWATHplus Grid Processor 3.05.19.0 Person who carried out this activity:
    Jane Denny
    U.S. Geological Survey
    Geologist
    384 Woods Hole Road
    Woods Hole, MA

    (508) 548-8700x2311 (voice)
    508-457-2310 (FAX)
    jdenny@usgs.gov
    Date: 2009 (process 5 of 15)
    Post-Processed Navigation (RTK corrections applied to DGPS data):
    The Ashtech Z-Xtreme receiver collected position (x,y) and elevation (z) data of the DGPS antenna during survey operations (see: Source Contribution for antenna configuration). DGPS position data (xyz) were recorded with HYPACK Hydrographic Survey Software (http://www.hypack.com/). Real-Time Kinematic (RTK) corrections based on vertical position data from the Fort Gratiot, Michigan National Geodetic Survey Continuously Operating Reference Stations (CORS) were applied to the recorded antenna heights (z) during post-processing using NovAtels Waypoint GrafNav post-processing high-precision package, a static kinematic/baseline processor (http://www.novatel.com/). A rover RTK-GPS station was established at the tidal benchmark at the U.S. Coast Guard Base at Port Huron in order to determine the offset between North American Vertical Datum of 1988 (NAVD 88) (vertical datum referenced at the CORS site) and the International Great Lakes Datum 1985 (IGLD 85) referenced at the tidal benchmark.
    An offset was applied to the RTK-corrected antenna heights to convert the reference heights to the local chart datum, International Great Lakes Datum 1985 (IGLD85). Additional offsets were applied to translate the height of the antenna to the waterline. The resulting data file contained date, time (every second) and height of waterline relative to IGLD85.
    (Navigation data are stored in American Standard Code for Information Interchange (ASCII) files. Offsets were applied using GNUs Not Unix (GNU) gawk 3.1.5 programming language).
    NovAtel GrafNav 8.1.0; GNU gawk 3.1.5; HYPACK 8.2.3.7 Person who carried out this activity:
    Jane Denny
    U.S. Geological Survey
    Geologist
    384 Woods Hole Road
    Woods Hole, MA

    (508) 548-8700x2311 (voice)
    508-457-2310 (FAX)
    jdenny@usgs.gov
    Date: 2009 (process 6 of 15)
    The date, time (every second) and height of waterline relative to IGLD85 were imported to The MathWorks MATLAB technical computing software (version 7.4.0 (R2007a)). A median filter (medfilt1) using a 361 boxcar (approximately a 6 minute filter) was applied to smooth the chatter present in the elevation data. The filtered elevations were then exported from MATLAB. A GNU gawk script was used to downsample the output file from every second to every minute:
    BEGIN { latmin = 0.0}{min= substr($1,4,2); if(lastmin !=min) {printf("%s %s %.2f\n", $1, $2, $3)} lastmin=min;}
    The filtered elevations at one-minute time intervals were then entered into SEA, LTD SWATHplus software as a Tide in the following format: HR:MN DD/MM/YYYY XXX.XX, where HR=hour, MN=minute, DD=day, MM= month, YYYY=year, XXX.XX=tide.
    MATLAB 7.4.0 (R2007a) Person who carried out this activity:
    Jane Denny
    U.S. Geological Survey
    Geologist
    384 Woods Hole Rd.
    Woods Hole, MA

    (508) 548-8700x2311 (voice)
    508-457-2310 (FAX)
    jdenny@usgs.gov
    Date: 2009 (process 7 of 15)
    Raw SXR bathymetry data were replayed line by line through the SEA SWATHplus software to generate processed SWATHplus sxp files. The following information was stored within the SWATHplus session files and applied to the raw bathymetric soundings: eight sound velocity profiles, TIDE (RTK-corrected water level heights relative to IGLD85), roll offsets calculated during pre-survey patch test, draft of the transducer below the water line, and the measured angles and relative positions of the swath bathymetric transducers. The SWATHplus software applies the pitch, roll, heave, and heading data supplied by the F180R IMU, to compensate depth solutions across the swath for any ship motion.
    Software: SWATHplus 3.05.19.0 Person who carried out this activity:
    Jane Denny
    U.S. Geological Survey
    Geologist
    384 Woods Hole Rd.
    Woods Hole, MA

    (508) 548-8700x2311 (voice)
    5084572310 (FAX)
    jdenny@usgs.gov
    Date: 2009 (process 8 of 15)
    All the processed SWATHplus sxp files were imported into CARIS HIPS/SIPS Hydrographic Data Processing System software (www.caris.com) using the CARIS HIPS Conversion Wizard (specifying the SWATHplus format, RawData (sxp files), a CARIS HIPS project, vessel, and julian day, ground coordinates [UTM zone 17N WGS84] and speed of sound of 1450 meters/second as measured at the SWATHplus transducer face). The conversion wizard converts depth, navigation, and motion data recorded in the sxp files into an internal CARIS HIPS format.
    The SXP files were then edited using the following filters: across track distance 7 times nadir depth (reduces the swath width to seven times the water depth in order to reduce noise in the outer range), across track angle of 2 degrees (calculates the slope of each beam in degrees to the prior and post beams within the same swath. If slopes exceed the specified value and are of opposite sign the beam is rejected), Missing neighbors: port and starboard, forward and aft, and any 2 of 4 (filters the soundings if neighboring soundings to the port and starboard, forward and aft, or if two of the four neighboring beams are missing) (http://www.caris.com). Individual files were further edited with the SWATH EDITOR where remaining outliers were manually removed.
    Field sheets were then created with UTM zone 17N, WGS84 projection and used to organize the processed bathymetric data and generate A Bathymetry Associated with Statistical Error (BASE) surfaces. Three BASE surfaces were created at the following resolutions: 0.5, 2.0 and 5.0 meters and the swath angle Surface Type (default). 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.
    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 Person who carried out this activity:
    Jane F. Denny
    U.S. Geological Survey
    Geologist
    384 Woods Hole Road
    Woods Hole, MA
    USA

    508-548-8700 x 2311 (voice)
    508-457-2310 (FAX)
    jdenny@usgs.gov
    Date: 2009 (process 9 of 15)
    Interactive Visualization Systems (IVS) Data Magician software (version 6.7.0k) was used to import the CARIS BASE surfaces. These data were imported as Gridded Data in the CARIS Base Surface File Type. The CARIS Base Surfaces were converted and saved in IVS dtm and geo format.
    The 0.5 m bathymetric grid contained data gaps at nadir. The filters used within the SWATHplus software eliminated noisy data near nadir, resulting in data gaps of less than 5 meters at nadir. To fill these data gaps, the IVS command dtmmerge from within the Fledermaus Commander was used to merge the high-resolution 0.5 meter grid with the lower resolution 2.0 grid.
    Dtmmerge in file1_highres.dtm file2_lowres.dtm out output.dtm cellsize 0.5
    By default, the lower resolution grid is used to fill data gaps present within the higher resolution grid, with the output grid reflecting the high-resolution input grid: 0.5 meters.
    After merging the 0.5- and 2.0-meter grids, several data gaps remained in areas where adjacent tracklines did not provide complete coverage of the riverbed. Dtmmerge was run again using the output from the first pass (merging the 0.5 and 2 meters grids) and the 5-m resolution grid in order to minimize data gaps between lines.
    The final grid, bathy_05m, was exported from IVS Data Magician as an Arcview Grid (ESRI ASCII grid) (bathy_05m_m.asc).
    Software: IVS DMagic 6.7.0 Person who carried out this activity:
    Jane F. Denny
    U.S. Geological Survey
    Geologist
    384 Woods Hole Road
    Woods Hole, MA
    USA

    508-548-8700 x 2311 (voice)
    508-457-2310 (FAX)
    jdenny@usgs.gov
    Date: 2009 (process 10 of 15)
    The ESRI ASCII grid (bathy_05m_m.asc) was then imported to ArcGIS 9.2 using the ASCII to Raster Tool within ArcToolbox - Conversion Tools - To Raster.
    The projection of the grids was then defined as UTM, zone 17N, WGS84, using Arc Toolbox, Data Management Tools, Projections and Transformations, Define Projection.
    In order to reduce spurious bathymetric points along the perimeter of the bathymetric grid, the border of the grid was digitized and saved as a polygon shapefile (border.shp). The Spatial Analyst Tool Extraction Extract by Mask was then used to clip the bathymetric grid (bathy_05m_m) based on the digitized border (border.shp), thus eliminating spurious points at the edges of the bathymetric grid. The output clipped grid was stored as bathy_05m.
    Software: ESRI ArcGIS 9.2 Person who carried out this activity:
    Jane F. Denny
    U.S. Geological Survey
    Geologist
    384 Woods Hole Road
    Woods Hole, MA
    USA

    508-548-8700 x 2311 (voice)
    508-457-2310 (FAX)
    jdenny@usgs.gov
    Date: 2010 (process 11 of 15)
    The bathymetric grid was converted from RASTER to ASCII using ArcGIS 9.2, ArcToolbox, Conversion Tools, From Raster, Raster to ASCII.
    ArcGIS 9.2 Person who carried out this activity:
    Jane Denny
    U.S. Geological Survey
    Geologist
    384 Woods Hole Road
    Woods Hole, MA
    USA

    508-548-8700 x 2311 (voice)
    508-457-2310 (FAX)
    jdenny@usgs.gov
    Date: 18-Oct-2017 (process 12 of 15)
    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.). The link to the data in the Identification_Information section had to be fixed. The link to the data in the Distribution_Information section had to be fixed. Fixed link to cross-reference. Attempted to modify http to https where appropriate. Reordered the links in the identification section to have a landing page link as the first link. 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. Added the AAIGrid distribution formation to account for the ASCII grid present in the zip file. 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. Person who carried out this activity:
    U.S. Geological Survey
    Attn: VeeAnn A. Cross
    Marine Geologist
    384 Woods Hole Road
    Woods Hole, MA

    508-548-8700 x2251 (voice)
    508-457-2310 (FAX)
    vatnipp@usgs.gov
    Date: 01-Dec-2017 (process 13 of 15)
    Keywords section of metadata optimized for discovery in USGS Coastal and Marine Geology Data Catalog. Person who carried out this activity:
    U.S. Geological Survey
    Attn: Alan O. Allwardt
    Contractor -- Information Specialist
    2885 Mission Street
    Santa Cruz, CA

    831-460-7551 (voice)
    831-427-4748 (FAX)
    aallwardt@usgs.gov
    Date: 18-Nov-2019 (process 14 of 15)
    Crossref DOI link was added as the first link in the metadata. Person who carried out this activity:
    U.S. Geological Survey
    Attn: VeeAnn A. Cross
    Marine Geologist
    384 Woods Hole Road
    Woods Hole, MA

    508-548-8700 x2251 (voice)
    508-457-2310 (FAX)
    vatnipp@usgs.gov
    Date: 23-Sep-2021 (process 15 of 15)
    Added keywords section with USGS persistent identifier as theme keyword 2020908. Fixed an original name 20210923. Person who carried out this activity:
    U.S. Geological Survey
    Attn: VeeAnn A. Cross
    Marine Geologist
    384 Woods Hole Road
    Woods Hole, MA

    508-548-8700 x2251 (voice)
    508-457-2310 (FAX)
    vatnipp@usgs.gov
  3. What similar or related data should the user be aware of?
    Foster, David S., and Denny, Jane F., 2009, Quaternary Geologic Framework of the St. Clair River between Michigan and Ontario, Canada: Open-File Report 2009-1137, U.S. Geological Survey, Reston, VA.

    Online Links:

How reliable are the data; what problems remain in the data set?

  1. How well have the observations been checked?
  2. How accurate are the geographic locations?
    Differential Global Positioning System (DGPS) navigation data were acquired with the forward, or primary, Octopus F180R Attitude and Positioning system DGPS antenna and transmitted via a network connection to the SWATHplus data collection software. The F180R Attitude and Positioning system uses 2 L1 antennas for position and heading and an Inertial Measurement Unit (IMU) for motion sensing. The F180R IMU is mounted on the rigid sidemount used to deploy the SWATHplus bathymetric system, and is located directly above the SWATHplus transducers. The F180R antennas are mounted on a rigid horizontal pole, 3 meters above the F180R IMU, offset in a forward/aft configuration (see 'source contribution' for a full description of the F180R). DGPS accuracy is 1 to 3 meters, depending on the distance from a US Coast Guard coastal repeater station (http://www.navcen.uscg.gov/).
  3. How accurate are the heights or depths?
    DGPS navigation was used to record horizontal and vertical position (x,y,z) of bathymetric soundings during data acquisition aboard the USGS R/V Rafael. An additional DGPS antenna, connected to an Ashtech Z-Xtreme receiver, was attached at the center of the rigid horizontal pole used to mount the Octopus F180R Attitude and Positioning system antennas. Real Time Kinematic GPS (RTK-GPS) corrections were applied to the Ashtech Z-Xtreme navigation data during post-processing in order to provide sub-meter vertical accuracy for bathymetric soundings. Fort Gratiot, MI, a Continuously Operating Reference Station (CORS) (http://www.ngs.noaa.gov/CORS/), was used as the reference station for the RTK-GPS corrections. A rover RTK-GPS station was established at the tidal benchmark at the U.S. Coast Guard Base at Port Huron in order to determine the offset between North American Vertical Datum of 1988 (NAVD 88) (vertical datum referenced at the CORS site) and the International Great Lakes Datum 1985 (IGLD 85) referenced at the tidal benchmark. The following offsets were applied to the shipboard DGPS data during post-processing: vertical offset between NAVD 88 and IGLD 85, the measured distance between the DGPS antenna and SWATHplus transducer, and the depth of the transducer below the water line. The resulting values were applied to the bathymetric soundings during processing to provide a measure of depth relative to IGLD 85.
  4. Where are the gaps in the data? What is missing?
    Lines 1 - 65 of swath bathymetric data were processed and used to generate the final bathymetric grid. Gaps present in this data set fall within shallow water areas where the swath width of the bathymetric system decreased to less than the 75-m survey trackline spacing. Data gaps at the beginning of survey lines 1 and 2 are due to deletion of poor quality data at the beginning of the line; the bathymetric system was not tracking bottom (i.e. the riverbed). Data gaps along the northeastern and southeastern edge of the survey are due to insufficient bottom coverage with the SWATHplus system.
  5. How consistent are the relationships among the observations, including topology?
    All bathymetric data were collected during USGS cruise 08016 using a SWATHplus 234-kHz swath bathymetric system and an Octopus F180R Attitude and Positioning System. Quality control was conducted during processing of the data. Any spurious data or artifacts were removed or minimized.

How can someone get a copy of the data set?

Are there legal restrictions on access or use of the data?
Access_Constraints: None
Use_Constraints:
These data are NOT to be used for navigation. Public domain data from the U.S. Government are freely redistributable with proper metadata and source attribution. Please recognize the U.S. Geological Survey as the originator of the dataset.
  1. Who distributes the data set? (Distributor 1 of 1)
    Jane Denny
    U.S. Geological Survey
    Geologist
    384 Woods Hole Road
    Woods Hole, MA
    USA

    508-548-8700 x2311 (voice)
    508-457-2310 (FAX)
    jdenny@usgs.gov
  2. What's the catalog number I need to order this data set? Downloadable Data
  3. What legal disclaimers am I supposed to read?
    Neither the U.S. Government, the Department of the Interior, nor the USGS, nor any of their employees, contractors, or subcontractors, make any warranty, express or implied, nor assume any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, nor represent that its use would not infringe on privately owned rights. The act of distribution shall not constitute any such warranty, and no responsibility is assumed by the USGS in the use of these data or related materials.
    Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government.
  4. How can I download or order the data?
  5. What hardware or software do I need in order to use the data set?
    The grid contained in the bathy_05m.zip file is available as an ESRI Binary grid and an ASCII grid with an ESRI header. However, the folder structure within bathy_05m.zip is critical to proper use of the ESRI binary grid.
    To utilize these data, the user must have a GIS software package capable of reading ESRI Binary grids or ASCII grids with ESRI headers, or be able to manipulate an ASCII matrix with a geospatial header. The ASCII raster files can be easily converted to ESRI grid format in either ArcView with Spatial Analyst extension (Import Data Source: ASCII Raster) or ArcGIS with Spatial Analyst extension (ASCII to Raster). The user should select floating point grid (as opposed to integer grid) when converting the bathymetry data.

Who wrote the metadata?

Dates:
Last modified: 23-Sep-2021
Metadata author:
U.S. Geological Survey
Attn: Jane F. Denny
Geologist
384 Woods Hole Road
Woods Hole, MA
USA

508-548-8700 x2311 (voice)
508-457-2310 (FAX)
jdenny@usgs.gov
Metadata standard:
FGDC Content Standards for Digital Geospatial Metadata (FGDC-STD-001-1998)
This page is <https://cmgds.marine.usgs.gov/catalog/whcmsc/open_file_report/ofr2010-1035/bathy_05m.faq.html>
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