4 meter sidescan-sonar GeoTIFF image of inner shelf with stretched histogram, from Cape Hatteras, NC to Cape Lookout, NC (composite_shatt_str.tif, UTM, Zone 18N, WGS84)

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Frequently anticipated questions:


What does this data set describe?

Title:
4 meter sidescan-sonar GeoTIFF image of inner shelf with stretched histogram, from Cape Hatteras, NC to Cape Lookout, NC (composite_shatt_str.tif, UTM, Zone 18N, WGS84)
Abstract:
The northeastern North Carolina coastal system, from False Cape, Virginia, to Cape Lookout, North Carolina, has been studied by a cooperative research program that mapped the Quaternary geologic framework of the estuaries, barrier islands, and inner continental shelf. This information provides a basis to understand the linkage between geologic framework, physical processes, and coastal evolution at time scales from storm events to millennia. The study area attracts significant tourism to its parks and beaches, contains a number of coastal communities, and supports a local fishing industry, all of which are impacted by coastal change. Knowledge derived from this research program can be used to mitigate hazards and facilitate effective management of this dynamic coastal system. This regional mapping project produced spatial datasets of high-resolution geophysical (bathymetry, backscatter intensity, and seismic reflection) and sedimentary (core and grab-sample) data. The high-resolution geophysical data were collected during numerous surveys within the back-barrier estuarine system, along the barrier island complex, in the nearshore, and along the inner continental shelf. Sediment cores were taken on the mainland and along the barrier islands, and both cores and grab samples were taken on the inner shelf. Data collection was a collaborative effort between the U.S. Geological Survey (USGS) and several other institutions including East Carolina University (ECU), the North Carolina Geological Survey, and the Virginia Institute of Marine Science (VIMS). The high-resolution geophysical data of the inner continental shelf were collected during six separate surveys conducted between 1999 and 2004 (four USGS surveys north of Cape Hatteras: 1999-045-FA, 2001-005-FA, 2002-012-FA, 2002-013-FA, and two USGS surveys south of Cape Hatteras: 2003-003-FA and 2004-003-FA) and cover more than 2600 square kilometers of the inner shelf. Single-beam bathymetry data were collected north of Cape Hatteras in 1999 using a Furuno fathometer. Swath bathymetry data were collected on all other inner shelf surveys using a SEA, Ltd. SwathPLUS 234-kHz bathymetric sonar. Chirp seismic data as well as sidescan-sonar data were collected with a Teledyne Benthos (Datasonics) SIS-1000 north of Cape Hatteras along with boomer seismic reflection data (cruises 1999-045-FA, 2001-005-FA, 2002-012-FA and 2002-013-FA). An Edgetech 512i was used to collect chirp seismic data south of Cape Hatteras (cruises 2003-003-FA and 2004-003-FA) along with a Klein 3000 sidescan-sonar system. Sediment samples were collected with a Van Veen grab sampler during four of the USGS surveys (1999-045-FA, 2001-005-FA, 2002-013-FA, and 2004-003-FA). Additional sediment core data along the inner shelf are provided from previously published studies. A cooperative study, between the North Carolina Geological Survey and the Minerals Management Service (MMS cores), collected vibracores along the inner continental shelf offshore of Nags Head, Kill Devils Hills and Kitty Hawk, North Carolina in 1996. The U.S. Army Corps of Engineers collected vibracores along the inner shelf offshore of Dare County in August 1995 (NDC cores) and July-August 1995 (SNL cores). These cores are curated by the North Carolina Geological Survey and were used as part of the ground validation process in this study. Nearshore geophysical and core data were collected by the Virginia Institute of Marine Science. The nearshore is defined here as the region between the 10-m isobath and the shoreline. High-resolution bathymetry, backscatter intensity, and chirp seismic data were collected between June 2002 and May 2004. Vibracore samples were collected in May and July 2005. Shallow subsurface geophysical data were acquired along the Outer Banks barrier islands using a ground-penetrating radar (GPR) system. Data were collected by East Carolina University from 2002 to 2005. Rotasonic cores (OBX cores) from five drilling operations were collected from 2002 to 2006 by the North Carolina Geological Survey as part of the cooperative study with the USGS. These cores are distributed throughout the Outer Banks as well as the mainland. The USGS collected seismic data for the Quaternary section within the Albemarle-Pamlico estuarine system between 2001 and 2004 during six surveys (2001-013-FA, 2002-015-FA, 2003-005-FA , 2003-042-FA, 2004-005-FA, and 2004-006-FA). These surveys used Geopulse Boomer and Knudsen Engineering Limited (KEL) 320BR Chirp systems, except cruise 2003-042-FA, which used an Edgetech 424 Chirp and a boomer system. The study area includes Albemarle Sound and selected tributary estuaries such as the South, Pungo, Alligator, and Pasquotank Rivers; Pamlico Sound and trunk estuaries including the Neuse and Pamlico Rivers; and back-barrier sounds including Currituck, Croatan, Roanoke, Core, and Bogue.
  1. How might this data set be cited?
    U.S. Geological Survey, 2013, 4 meter sidescan-sonar GeoTIFF image of inner shelf with stretched histogram, from Cape Hatteras, NC to Cape Lookout, NC (composite_shatt_str.tif, UTM, Zone 18N, WGS84): Open-File Report 2011-1015, 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.

    Thieler, E.R., Foster, D.S., Mallinson, D.M., Himmelstoss, E.A., McNinch, J.E., List, J.H., and Hammar-Klose, E.S., 2013, Quaternary Geophysical Framework of the Northeastern North Carolina Coastal System: Open-File Report 2011-1015, U.S. Geological Survey, Reston, VA.

    Online Links:

  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -76.538429
    East_Bounding_Coordinate: -75.479329
    North_Bounding_Coordinate: 35.237621
    South_Bounding_Coordinate: 34.503150
  3. What does it look like?
  4. Does the data set describe conditions during a particular time period?
    Beginning_Date: 17-Jun-2003
    Ending_Date: 09-Jul-2004
    Currentness_Reference:
    ground condition
  5. What is the general form of this data set?
    Geospatial_Data_Presentation_Form: remote-sensing image
  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 20125 x 24000 x 1, type Pixel
    2. What coordinate system is used to represent geographic features?
      Grid_Coordinate_System_Name: Universal Transverse Mercator
      Universal_Transverse_Mercator:
      UTM_Zone_Number: 18
      Transverse_Mercator:
      Scale_Factor_at_Central_Meridian: 0.999600
      Longitude_of_Central_Meridian: -75.000000
      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 4.000000
      Ordinates (y-coordinates) are specified to the nearest 4.000000
      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.
  7. How does the data set describe geographic features?
    Entity_and_Attribute_Overview:
    There are no attributes associated with a GeoTIFF image. Image pixel values contain acoustic reflectivity values normalized to an 8-bit data range (0-255) with the data range 0-254. Low-backscatter is represented by dark tones (low values) and high-backscatter is represented by bright tones (high values). The background color is set to 255 and can be turned off without removing data values. This does not include small areas of NODATA within the sidescan mosaic.
    Entity_and_Attribute_Detail_Citation: U.S. Geological Survey

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?
    E. Robert Thieler
    U.S. Geological Survey
    Research Geologist
    384 Woods Hole Road
    Woods Hole, MA
    USA

    508-548-8700 x2350 (voice)
    508-457-2310 (FAX)
    rthieler@usgs.gov

Why was the data set created?

This GeoTIFF contains sidescan-sonar backscatter data from the southern half of the inner continental shelf study area from Cape Hatteras to Cape Lookout, NC. Grayscale values correspond to the varied strength of the returned beam signal. The intensity of the sound received from the seafloor by the sonar tow vehicle (backscatter) is digitally represented as light-tones (high backscatter) and dark tones (low backscatter) within the grayscale GeoTIFF. High backscatter indicates a strong reflection off the seafloor and generally can be associated with coarse-grained material. Low backscatter represents a weak reflection off the seafloor and is generally associated with finer-grained material.

How was the data set created?

  1. From what previous works were the data drawn?
    Information unavailable from original metadata. (source 1 of 2)
    U.S. Geological Survey, unknown, Information unavailable from original metadata..

    Type_of_Source_Media: disc
    Source_Contribution:
    Data acquisition at sea: Sidescan-sonar data were collected with a Klein 3000 (100/500 kHz dual frequency) sidescan-sonar towfish and digitally recorded using Edgetech SonarPro acquisition software in XTF format. The raw sidescan-sonar files were converted from *.xtf to *.dat format using a Windows DOS script. The *.dat format is directly readable by the XSonar/ShowImage processing software. During the surveys the sonar was towed from the stern A-frame of either the R/V Atlantic Surveyor (2003) or the Megan T Miller (2004). Data were acquired roughly parallel to the shoreline at an average speed of 5 knots.
    Information unavailable from original metadata. (source 2 of 2)
    The source information was incomplete and had to be modified to meet the standard. Assumed to be USGS., unknown, Information unavailable from original metadata..

    Type_of_Source_Media: Information unavailable from original metadata.
    Source_Contribution: Information unavailable from original metadata.
  2. How were the data generated, processed, and modified?
    Date: unknown (process 1 of 11)
    Sidescan-sonar data were collected using a Klein 3000 (100/500 kHz dual frequency) sidescan-sonar towfish and digitally recorded using Edgetech SonarPro acquisition software in XTF format. Person who carried out this activity:
    E. Robert Thieler
    U.S. Geological Survey
    Geologist
    384 Woods Hole Road
    Woods Hole, MA
    USA

    508-548-8700 x2250 (voice)
    508-457-2310 (FAX)
    rthieler@usgs.gov
    Date: Oct-2003 (process 2 of 11)
    Within XSonar/ShowImage Processing Software a median filtering routine (4 pixels across track by 3 pixels along track) was applied to the raw sidescan-sonar data to remove speckle noise (Danforth and others, 1991). The data were further processed to correct for fish altitude, slant range and beam pattern artifacts, and merged with the navigation after the data were edited for spurious fixes (Danforth, 1997). Adjacent sidescan-sonar lines were mapped into two separate mosaics (north-heading and south-heading) at 2 meter/pixel resolution using Xsonar/Showimage. The survey area was divided into subareas with similar line orientations and to keep file sizes manageable. This process step and all subsequent process steps were performed by the same person: Emily Himmelstoss. Person who carried out this activity:
    Emily Himmelstoss
    U.S. Geological Survey
    Geologist
    384 Woods Hole Road
    Woods Hole, MA
    USA

    508-548-8700 x2262 (voice)
    508-457-2310 (FAX)
    ehimmelstoss@usgs.gov
    Date: 2004 (process 3 of 11)
    PCI Geomatica is a commercially available software package used to digitally mosaic sidescan-sonar data. A PCI Geomatica project was created for subareas of the inner shelf of North Carolina (16 total). The north and south-heading working mosaics were imported into PCI Geomatica and digitally mosaicked using PCI's OrthoEngine following procedures described in Paskevich (1992, 1996). The geographically-oriented raster imagery (north-heading and south-heading) for each area were imported as separate files. Adjacent sidescan-sonar records were compared to establish ground control points at common target locations. This helps to correct for navigational errors and potential feature offset due to undefined layback of the tow vehicle. The north-heading mosaic was used as the control and a stencil line was drawn around individual swath records in the south-heading mosaic to cut and paste on an adjacent swath in the north-heading mosaic. This procedure was repeated for each south-heading sidescan-sonar line to form a composite digital mosaic of the subarea. The final mosaic was exported as a TIFF image, with an associated world file. The mosaicking process produced an enhanced, geographically correct, sidescan-sonar mosaic with 2 meter/pixel resolution (UTM Zone 18N, WGS84) for each of the sixteen subareas.
    Date: Nov-2004 (process 4 of 11)
    The sixteen individual subarea mosaics were then compiled into two larger composite images within PCI Geomatica. Individual subarea files numbered 13 through 16 were imported into the composite image south by defining their position in pixel space. Stencil lines were again used to cut and paste adjacent areas to create a sidescan-sonar composite. The composite mosaic of sidescan-sonar south of Cape Hatteras, was exported as a GeoTIFF image at 4 meter/pixel resolution.
    Date: 11-May-2011 (process 5 of 11)
    An offset was discovered in area 14 of the composite backscatter image and was re-mosaicked using PCI Geomatica (v.10.1). The original area 14 mosaic was quality checked and confirmed to be properly georeferenced. It is assumed an offset error was introduced during the compilation of the composite mosaic. The composite mosaic TIFF was imported to a new project file using the Orthoengine. A new stencil line was drawn to cut and replace the problem area with the originally-processed subarea file. The file was then exported as a GEOTIFF.
    Date: 12-May-2011 (process 6 of 11)
    Most of the NODATA area in the GeoTIFF image (outside the survey bounds) has a pixel value of 255. But as a result of the mosaicking process, some areas of NODATA have a pixel value of 254. Using Adobe Photoshop (CS5), all of the NODATA areas were selected and assigned a single NODATA value of 255. All backscatter data within the survey area have pixel values ranging from 0 to 254 although some small data gaps (NODATA) do occur within the survey area as well.
    Date: 12-May-2011 (process 7 of 11)
    A linear contrast stretch was applied to the final composite mosaic using Photoshop (CS5). The lightest and darkest pixel levels were clipped to the upper and lower limits of the image's histogram. This redistributed the remaining levels between 0-254 (note in last step NODATA were given a unique value of 255). This redistribution increases the tonal range of the image, improving the visual contrast between areas that originally had small tonal differences.
    Date: 10-Jun-2016 (process 8 of 11)
    Edits to the metadata were made to fix any errors that MP v 2.9.32 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 catalog was fixed. Online links were added to the cross-references. A link in the Completeness_Report was fixed. The source information was incomplete and had to be modified to meet the standard. 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. Person who carried out this activity:
    U.S. Geological Survey
    Attn: VeeAnn A. Cross
    Marine Geologist
    384 Woods Hole Rd.
    Woods Hole, MA

    508-548-8700 x2251 (voice)
    508-457-2310 (FAX)
    vatnipp@usgs.gov
    Date: 20-Jul-2018 (process 9 of 11)
    USGS Thesaurus keywords added to the keyword section. 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: 18-Nov-2019 (process 10 of 11)
    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: 08-Sep-2020 (process 11 of 11)
    Added keywords section with USGS persistent identifier as theme keyword. 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?
    Danforth, W.W., O'Brien, T.F., and Schwab, W.C., 1991, USGS image processing system: near real-time mosaicking of high-resolution sidescan-sonar data: Sea Technology Jan. 1991, Sea Technology, Arlington, VA.

    Danforth, W.W., 1997, Xsonar/ShowImage; a complete system for rapid sidescan-sonar processing and display: Open-File Report 1997-686, U.S. Geological Survey, Reston, VA.

    Online Links:

    Paskevich, V.F., 1992, Digital mapping of sidescan sonar data with the Woods Hole Image Processing System software: Open-File Report 92-536, U.S. Geological Survey, Reston, VA.

    Online Links:

    Paskevich, Valerie, 1996, MAPIT: An improved method for mapping digital sidescan sonar data using the Woods Hole Image Processing System (WHIPS) Software: Open-File Report 96-281, 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?
    Image pixel values contain acoustic reflectivity values normalized to an 8-bit data range (0-255). Low-backscatter is represented by dark tones (low values) and high-backscatter is represented by bright tones (high values).
  2. How accurate are the geographic locations?
    The Klein 3000 was towed from the stern A-frame of the survey vessel (R/V Atlantic Surveyor in 2003 and R/V Megan T. Miller in 2004). Differential GPS (DGPS) was recorded to the raw data files (XTF) on the sonar acquisition computer. Layback (the linear distance between the shipboard DGPS receiver and the towed sonar vehicle) was estimated to be 100 meters and accounted for during processing. Positional uncertainty arises because the layback is estimated, not measured directly, and does not account for fish motion behind the vessel, which can be caused by sea state and vessel speed-induced changes in the angle and scope of the tow cable.
  3. How accurate are the heights or depths?
  4. Where are the gaps in the data? What is missing?
    Only the subset of sidescan-sonar backscatter data collected south of Cape Hatteras have been included in this spatial dataset. Additional sidescan-sonar backscatter data collected north of Cape Hatteras are included in a separate file (http://pubs.usgs.gov/of/2011/1015/data/backscatter/innershelf/composite_nhatt_str.zip). Some sections of sonar data with excess noise were clipped during processing. Variable sea state and weather conditions introduced noise in the sonar record resulting in tonal variations (artifacts) within the composite sonar image.
  5. How consistent are the relationships among the observations, including topology?
    This image represents shore-parallel sidescan-sonar data; no crossline data were included in this image. Gaps may occur along-track due to system malfunction and between adjacent lines due to obstacle avoidance.

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:
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)
    E. Robert Thieler
    U.S. Geological Survey
    Research Geologist
    384 Woods Hole Road
    Woods Hole, MA
    USA

    508.548.8700 x2350 (voice)
    508.457.2310 (FAX)
    rthieler@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 U.S. Geological Survey 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?
    This zip file contains a GeoTIFF image with an accompanying world file. To utilize this data, the user must have an image viewer, image processing or GIS software package capable of importing a GeoTIFF image. A free spatial data viewer, ArcExplorer, capable of displaying the data is available from ESRI at www.esri.com.

Who wrote the metadata?

Dates:
Last modified: 08-Sep-2020
Metadata author:
Emily Himmelstoss
U.S. Geological Survey
Geologist
384 Woods Hole Road
Woods Hole, MA
USA

508-548-8700 x2262 (voice)
508-457-2310 (FAX)
ehimmelstoss@usgs.gov
Metadata standard:
FGDC Content Standards for Digital Geospatial Metadata (FGDC-STD-001-1998)

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