CON_1M - Bathymetric Contours within the inner shelf of Long Bay, South Carolina (1 meter interval: Polyline)

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Frequently-anticipated questions:


What does this data set describe?

Title:
CON_1M - Bathymetric Contours within the inner shelf of Long Bay, South Carolina (1 meter interval: Polyline)
Abstract:
In 1999, the USGS, in partnership with the South Carolina Sea Grant Consortium, began a study to investigate processes affecting shoreline change along the northern coast of South Carolina, focusing on the Grand Strand region. Previous work along the U.S. Atlantic coast shows that the structure and composition of older geologic strata located seaward of the coast heavily influences the coastal behavior of areas with limited sediment supply, such as the Grand Strand. By defining this geologic framework and identifying the transport pathways and sinks of sediment, geoscientists are developing conceptual models of the present-day physical processes shaping the South Carolina coast. The primary objectives of this research effort are: 1) to provide a regional synthesis of the shallow geologic framework underlying the coastal upland, shoreface and inner continental shelf, and define its role in coastal evolution and modern beach behavior; 2) to identify and model the physical processes affecting coastal ocean circulation and sediment transport, and to define their role in shaping the modern shoreline; and 3) to identify sediment sources and transport pathways; leading to construction of a regional sediment budget.
  1. How should this data set be cited?

    U.S. Geological Survey, 2007, CON_1M - Bathymetric Contours within the inner shelf of Long Bay, South Carolina (1 meter interval: Polyline): Open-File Report 2005-1346, U.S. Geological Survey, Coastal and Marine Geology Program, Woods Hole Science Center, Woods Hole, MA.

    Online Links:

    This is part of the following larger work.

    Baldwin, W.E., Denny, J.F., Schwab, W.C., Gayes, P.T., Morton, R.A., and Driscoll, N.W., 2007, Geologic Framework Studies of South Carolina's Long Bay from Little River Inlet to Winyah Bay, 1999-2003; geospatial data release: Open-File Report 2005-1346, U.S. Geological Survey, Coastal and Marine Geology Program, Woods Hole Science Center, Woods Hole, MA.

    Online Links:

  2. What geographic area does the data set cover?

    West_Bounding_Coordinate: -79.157353
    East_Bounding_Coordinate: -78.520183
    North_Bounding_Coordinate: 33.854991
    South_Bounding_Coordinate: 33.191807

  3. What does it look like?

    <http://pubs.usgs.gov/of/2005/1346/images/con_1m.jpg> (JPEG)
    color coded image of bathymetry

  4. Does the data set describe conditions during a particular time period?

    Beginning_Date: 1999
    Ending_Date: 2003
    Currentness_Reference: ground condition

  5. What is the general form of this data set?

    Geospatial_Data_Presentation_Form: vector digital data

  6. How does the data set represent geographic features?

    1. How are geographic features stored in the data set?

      This is a Point data set. It contains the following vector data types (SDTS terminology):

      • String (215)

    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 coordinate pair
      Abscissae (x-coordinates) are specified to the nearest 0.000128
      Ordinates (y-coordinates) are specified to the nearest 0.000128
      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:
      Depth_System_Definition:
      Depth_Datum_Name: Mean lower low water
      Depth_Resolution: 1
      Depth_Distance_Units: meters
      Depth_Encoding_Method: Attribute values

  7. How does the data set describe geographic features?

    con_1m
    1 meter contour interval (Source: ESRI)

    FID
    Internal feature number. (Source: ESRI)

    Sequential unique whole numbers that are automatically generated.

    Shape
    Feature geometry. (Source: ESRI)

    Coordinates defining the features.

    ID
    Internal ID (Source: ESRI)

    Range of values
    Minimum:1
    Maximum:215
    Units:integer count
    Resolution:1

    CONTOUR
    Contour label (Source: USGS)

    Range of values
    Minimum:-13
    Maximum:-3
    Units:meters
    Resolution:1


Who produced the data set?

  1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)

  2. Who also contributed to the data set?

  3. To whom should users address questions about the data?

    U.S. Geological Survey
    c/o Jane Denny
    Geologist
    384 Woods Hole Road
    Woods Hole, MA 02543-1598
    USA

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


Why was the data set created?

This data set contains 1 meter contours generated from the swath bathymetric data collected between 1999 and 2003. These data are used to define the sea-floor morphology offshore of the Grand Strand, South Carolina.


How was the data set created?

  1. From what previous works were the data drawn?

  2. How were the data generated, processed, and modified?

    Date: 2004 (process 1 of 6)
    Bathymetric data were corrected for variations in the speed of sound throughout the water column; sound velocity profiles were acquired throughout the survey area using an Applied MicroSystems SVPlus Sound Velocimeter. These data were downloaded and reformatted to the required format needed for use within University of New Brunswick's Ocean Mapping Group (OMG) SwathEd multibeam processing software. The raw Submetrix 2000 Series data were "unraveled" and reformatted into the OMG format. This process creates several files on disk:
    1) bathymetric soundings 2) raw sidescan-sonar backscatter 3) navigation 4) parameter files describing the configuration of the system (i.e. offsets between motion reference unit and GPS antenna, etc).
    This process also incorporates the sound velocity profiles in order to properly trace the rays given the structure of the water column.

    Person who carried out this activity:

    Jane Denny
    U.S. Geological Survey
    Geologist
    384 Woods Hole Road
    Woods Hole, MA 02543-1598
    USA

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

    Date: 2004 (process 2 of 6)
    The OMG formatted bathymetric data were then graphically edited using the SwathEd multibeam processing software. This enabled editing on a "ping-by-ping" basis, both in the across- and along-track dimension. Spurious or erroneous data were removed. The navigation data were also graphically examined for each line of data.

    Person who carried out this activity:

    Jane Denny
    U.S. Geological Survey
    Geologist
    384 Woods Hole Road
    Woods Hole, MA 02543-1598
    USA

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

    Date: 2004 (process 3 of 6)
    Navigation data output during the unravel were reformatted for entry into MATLAB. The time of day and position were used to extract the tidal elevation from within the ADCIRC circulation model. The ADCIRC circulation model is referenced to Mean Sea Level. Verified tidal data from the NOAA tidal gauge at SpringMaid Pier, SC were downloaded, referenced to Mean Lower Low Water (MLLW). A low-pass filter was applied to the NOAA tide data; the residual was assumed to represent the wind component of sea surface elevations. Tidal elevation (output from ADCIRC) and wind component (NOAA tide station) represent total variation in surface elevations. These data were then written to an ASCII file and reformatted to OMG format for use within SwathEd. The tidal data were then written into the headers of the OMG formatted files, using the 'mergedTide' command.
    (SwathEd Commands:
    binTide -year XXX adcirc_wind.txt tide.bin mergeTide -tide tide.bin *.merged
    )
    SwathEd Software was used to grid the bathymetric data at 20 m grid cell size utilizing the 'weigh_grid' command.
    weigh_grid -omg -butter -power 2 -cutoff 10 -lambda 2.5 Grid *.merged
    The gridded data were then viewed using the SwathEd Jview Command. The PatchTool was used to assess the roll misalignment of the data; slight roll misalignment artifacts were visible in the gridded data. The PatchTool is a QC tool to assess the degree to which the head (transducers and MRU) needs to be 'rolled' to achieve the proper alignment. QC was also preformed on the navigation. Edits were made as necessary. After the needed adjustments were recorded, the configuration and navigation were remerged with the OMG bathymetric data using the mergeNav and mergeAtt commands.
    mergeNav -use_params 0 -nav *.nav -swath *.merged)
    The remerged data were regridded for a second round of QC. The roll misalignment artifacts were no longer visible in the gridded data.
    The bathymetric data to this point have been edited, navigation, edited, tidal elevations relative to MLLW incorporated in the data, sound velocity corrections applied, and roll misalignment rectified. Next the data need to be interpolated to generate a continuous bathymetric surface.
    The SwathEd 'make_blank' command was used to generate a 20 meter grid for the survey area. The OMG formatted bathymetric files were then written into the 20 meter grid using the 'weigh_grid' command. Due to noise within the far range of the sonar signal, the 'max_incidence' parameter was used. This essentially limits the across track data range of the data; thus elimination noise.
    (weigh_grid -omg -butter -power 2 -cutoff 20 -lambda 10 -max_incidence 60 Grid *.merged)
    The 20 meter gridded data were then exported to an xyz ASCII file.
    (r4toASCII -utm -merid -81 20m_grd 20m.xyz)

    Person who carried out this activity:

    Jane Denny
    U.S. Geological Survey
    Geologist
    384 Woods Hole Road
    Woods Hole, MA 02543-1598
    USA

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

    Date: 2004 (process 4 of 6)
    The 20m xyz ASCII data were then imported into Geographic Resources Analysis Support System (GRASS). A spline with tension and directionality interpolation routine was used in order to generate a continuous bathymetric surface from the interferometric sonar data. After many iterations, the gridding parameters resulting in a gridded dataset with the least amount of visible artifacts were as follows:
    s.surf.rst input=20m.xyz elev=grid100m field=1 tension=200 dmin=20 theta=45 scalex=0.5 smooth=2
    A smoothing filter (comparable to a median/mean filter) was applied to the dataset.

    Person who carried out this activity:

    Jane Denny
    U.S. Geological Survey
    Geologist
    384 Woods Hole Road
    Woods Hole, MA 02543-1598
    USA

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

    Date: 2004 (process 5 of 6)
    The final grid was then exported as an ESRI Binary Grid.
    r.out.arc in=grid100m out=grid100m.asc
    The exported data were then imported to ArcGIS 9.0 using the ASCIItoGRID command. The projection was then defined: UTM, zone 17 projection, WGS84 Ellipsoid.

    Person who carried out this activity:

    Jane Denny
    U.S. Geological Survey
    Geologist
    384 Woods Hole Road
    Woods Hole, MA 02543-1598
    USA

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

    Date: 2004 (process 6 of 6)
    1 meter contours were generated by contouring the bathymetric grid. Manual edits were made where necessary.

    Person who carried out this activity:

    Jane Denny
    U.S. Geological Survey
    Geologist
    384 Woods Hole Road
    Woods Hole, MA 02543-1598
    USA

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

    Data sources used in this process:
    • bathy_grd

    Data sources produced in this process:

    • con_1m.dbf
    • con_1m.shp
    • con_1m.shx

  3. What similar or related data should the user be aware of?


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

  1. How well have the observations been checked?

    These data are internally consistent and have been compared to multibeam and single-beam bathymetric surveys to check for accuracy. Any differences between this bathymetric data set and others were determined to be within acceptable error given the inherent differences in the various bathymetric data sets (i.e. acquisition system, mode of navigation, density of point, and or swath bathymetry).

  2. How accurate are the geographic locations?

    DGPS is assumed to be accurate within 1-2 meters. Standard GPS is assumed accurate within 5-10 meters. 99% of the positional data is DGPS. Unless noted, all GPS/DGPS data is referenced to WGS84 (NAD83). The configuration of the fathometer is as follows: The fathometer is mounted on either the port or starboard side of the vessel. Offset between the sidemount and GPS antennae is measured. No measurements were taken of ship's pitch, yaw, heave, or change in draft due to water and fuel usage. Motion of the fathometer is not measured. Horizontal accuracy of the fathometer is assumed to be within 3 meters.

  3. How accurate are the heights or depths?

    Ship motion was recorded with a TSS DMS 2-05 Attitude Sensor, mounted directly above the SEA SwathPlus transducers. Navigation was recorded using a Differential Global Positioning System (DGPS). The interferometric sonar is an angle-measuring system; depth accuracy decreases with increasing horizontal range. The combined angular accuracy of the SwathPlus system and the TSS DMS 2-05 attitude sensor is documented as 0.1 degrees. Assuming a constant angular accuracy, and using the International Hydrographic Standard (IHO) of a required 0.3 meter accuracy in < 30 meter water depth, all data collected within the survey fall within the IHO accuracy standards. However, vertical accuracy is also directly affected by the accuracy of both the navigation system and tidal measurements.

  4. Where are the gaps in the data? What is missing?

    The data contain 1-meter bathymetric contours generated from the bathymetric grid. They contain all data collected during USGS field efforts offshore of Myrtle Beach, SC 1999 2003.

  5. How consistent are the relationships among the observations, including topology?

    These data were checked for consistency by plotting the point data with the contoured surface and eliminating spurious and anomalous soundings. No additional checks for topological consistency were performed on these data.


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)

    U.S. Geological Survey
    384 Woods Hole Road
    Woods Hole, MA 02543-1598
    USA

    508-548-8700 (voice)
    508-457-2310 (FAX)

  2. What's the catalog number I need to order this data set?

    Downloadable Data

  3. What legal disclaimers am I supposed to read?

    Although all data have been used by the USGS, no warranty, expressed or implied, is made by the USGS as to the accuracy of the data and/or related materials. 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?

    These data are available in Environmental Systems Research Institute (ESRI) polyline shapefile format. The user must have ArcGIS or ArcView 3.0 or greater software to read and process the data file. In lieu of ArcView or ArcGIS, the user may utilize another GIS application package capable of importing the data. A free data viewer, ArcExplorer, capable of displaying the data is available from ESRI at www.esri.com.


Who wrote the metadata?

Dates:
Last modified: 23-Jan-2007
Metadata author:
Jane Denny
U.S. Geological Survey
Geologist
384 Woods Hole Road
Woods Hole, MA 02543-1598
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)
Metadata extensions used:


Generated by mp version 2.9.2 on Tue Mar 06 14:47:06 2007