Composite Sidescan-Sonar Mosaic, Pulley Ridge: Geographic Coordinate System

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Frequently-anticipated questions:

What does this data set describe?

Title:
Composite Sidescan-Sonar Mosaic, Pulley Ridge: Geographic Coordinate System
Abstract:
Pulley Ridge is a series of drowned barrier islands that extends almost 200 km in 60-100 m water depths. This drowned ridge is located on the Florida Platform in the southeastern Gulf of Mexico about 250 km west of Cape Sable, Florida. This barrier island chain formed during the initial stage of the Holocene marine transgression. These islands were then submerged and left abandoned near the outer edge of the Florida Platform. The southern portion of Pulley Ridge hosts zooxanthellate scleractinian corals, green, red and brown macro algae, and a mix of deep and typically shallow-water tropical fishes. This reef community is in unusually deep water, and its extent and the controls on its distribution were unknown. To address these questions scientists from the U.S. Geological Survey Coastal and Marine Geology Program in cooperation with scientists from the University of South Florida Department of Marine Sciences have completed a detailed mapping of the southernmost 35 km of Pulley Ridge. The area was mapped using multibeam bathymetry, sidescan-sonar imagery, and high-resolution seismic-reflection profiling to define the geologic framework on which the reef is established. Submersible dives, remotely operated vehicle (ROV) transects, and transects of bottom photographs and video were collected to identify the corals and to map their distribution. This extensive suite of data has been compiled and preliminary analysis of the data suggests that the reefs are not tied to the ridge system, but instead are more broadly distributed. Whether reef distribution is controlled by oceanographic conditions or by subtle differences in the substrate that overlies the barrier island system is unclear, and are topics of continued research.
  1. How should this data set be cited?

    Twichell, David C. , and Cross, VeeAnn A. , 2005, Composite Sidescan-Sonar Mosaic, Pulley Ridge: Geographic Coordinate System:.

    Online Links:

    This is part of the following larger work.

    Cross, VeeAnn A. , Twichell, David C. , Halley, Robert B. , Ciembronowicz, Kate T. , Jarrett, Bret D. , Hammar-Klose, Erika S. , Hine, Al C. , Locker, Stan D. , and Naar, Dave F. , 2005, GIS Compilation of Data Collected from the Pulley Ridge Deep Coral Reef Region: Open-File Report 2005-1089, 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: -83.787795
    East_Bounding_Coordinate: -83.592758
    North_Bounding_Coordinate: 25.001414
    South_Bounding_Coordinate: 24.648368

  3. What does it look like?

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

    Beginning_Date: 07-Sep-2001
    Ending_Date: 08-Sep-2001
    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 39107 x 19608 x 1, type Pixel

    2. What coordinate system is used to represent geographic features?

      Horizontal positions are specified in geographic coordinates, that is, latitude and longitude. Latitude and longitude values are specified in Decimal degrees.

      The horizontal datum used is North American Datum of 1983.
      The ellipsoid used is Geodetic Reference System 80.
      The semi-major axis of the ellipsoid used is 6378137.000000.
      The flattening of the ellipsoid used is 1/298.257222.

  7. How does the data set describe geographic features?

    Band_1

    ObjectID
    Internal feature number. (Source: ESRI)

    Sequential unique whole numbers that are automatically generated.

    Value

    Red

    Green

    Blue

    Entity_and_Attribute_Overview:
    The pixel value represents the DN return value of the sidescan-sonar system. A high value (i.e. 254) indicates a highly reflective sea floor surface, while a low value (i.e. 0) indicates low reflectance. All of the sidescan-sonar imagery was collected at a 600 m swath.

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?

    David C. Twichell
    U.S. Geological Survey
    Oceanographer
    384 Woods Hole Rd.
    Woods Hole, MA 02543-1598

    (508) 548-8700 x2266 (voice)
    (508) 457-2310 (FAX)
    dtwichell@usgs.gov

Why was the data set created?

This sidescan-sonar mosaic is used to map the morphology of the seafloor.

How was the data set created?

  1. From what previous works were the data drawn?

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

    (process 1 of 7)
    Sidescan-sonar imagery was collected using an EG&G DF1000 sidescan sonar system and logged to a Triton Elics QMIPS data logging computer.

    Person who carried out this activity:

    Erika Hammar-Klose
    U.S. Geological Survey
    Marine Geologist
    384 Woods Hole Rd.
    Woods Hole, MA 02543-1598

    (508) 548-8700 x2344 (voice)
    5084572310 (FAX)
    ehammark@usgs.gov

    (process 2 of 7)
    The digital sidescan data were then processed and mapped to provide proper geographic locations of features identified in the imagery. The processing steps included subsampling the raw sidescan data using a median filtering routine to suppress speckle noise and reduce file size, and correct for slant-range distortion, signal attenuation, and dropped sonar lines using XSonar (Danforth et al., 1991). After these processing steps, the imagery was mapped into its proper geographic location using techniques summarized by Paskevich (1996). Individual sidescan swaths were mapped with each pixel geographically positioned at a resolution of 1 m/pixel.

    Person who carried out this activity:

    Erika Hammar-Klose
    U.S. Geological Survey
    Marine Geologist
    384 Woods Hole Rd.
    Woods Hole, MA 02543-1598

    (508) 548-8700 x2344 (voice)
    5084572310 (FAX)
    ehammark@usgs.gov

    (process 3 of 7)
    Non-overlapping swaths were then brought into the remote sensing software package PCI. The techniques for generating the composite digital sidescan mosaic are summarized by Paskevich (1992).

    (process 4 of 7)
    Once the mosaics were completed, noise and areas of no data were trimmed from the fringes of the completed mosaic.

    Person who carried out this activity:

    VeeAnn A. Cross
    U.S. Geological Survey
    Marine Geologist
    384 Woods Hole Rd.
    Woods Hole, MA 02543-1598

    (508) 548-8700 x2251 (voice)
    (508) 457-2310 (FAX)
    vatnipp@usgs.gov

    (process 5 of 7)
    A linear stretch was applied in PCI to the sidescan image. This stretch was from 0-255 with resulting values between 0 and 254. This was done so that the white background (255) could be made transparent in the GIS.

    Person who carried out this activity:

    VeeAnn A. Cross
    U.S. Geological Survey
    Marine Geologist
    384 Woods Hole Rd.
    Woods Hole, MA 02543-1598

    (508) 548-8700 x2251 (voice)
    (508) 457-2310 (FAX)
    vatnipp@usgs.gov

    (process 6 of 7)
    The individual mosaics from areas a, b, and c were combined into a composite mosaic using BlueMarble's Geographic Transformer version 5.1.

    (process 7 of 7)
    This composite mosaic was reprojected to geographic coordinates using BlueMarble's Geographic Transformer, version 5.1. The central latitude was auto-computed (24deg 49' 29.65"N).

  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: Jan. 1991, Sea Technology.

    Hammar-Klose, E.S., Twichell, D.C., and Worley, C.R., 2003, Archive of sidescan-sonar data and DGPS navigation data, collected during USGS cruise SUNC01010, Pulley Ridge, Gulf of Mexico, 05 September - 12 September 2001: Open-File Report 02-155, U.S. Geological Survey, Woods Hole Science Center, Woods Hole, MA.

    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.

    Paskevich, V.F., 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.

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?

    The ship was navigated with Differential GPS which has an assumed accuracy of better than 10 meters. A transponder was used to range to fish, which introduces additional positional accuracy of the sidescan imagery.

  3. How accurate are the heights or depths?

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

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

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:
The U.S. Geological Survey must be referenced as the originator of the dataset in any future products or research derived from these data.

  1. Who distributes the data set? (Distributor 1 of 1)

    David C. Twichell
    U.S. Geological Survey
    Oceanographer
    384 Woods Hole Rd.
    Woods Hole, MA 02543-1598

    (508) 548-8700 x2266 (voice)
    (508) 457-2310 (FAX)
    dtwichell@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?

    These data were prepared by an agency of the United States Government. Neither the United States government nor any agency thereof, nor any of their employees, make any warranty, expressed or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed in this report, or represents that its use would not infringe privately owned rights. Reference therein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States government or any agency thereof. Any views and opinions of authors expressed herein do not necessarily state or reflect those of the United States government or any agency thereof. Although all data published in this report have been used by the USGS, no warranty, expressed or implied, is made by the USGS as to the accuracy of the data and related materials and/or the functioning of the software. The act of distribution shall not constitute any such warranty, and no responsibility is assumed by the USGS in the use of this data, software, or related materials.

  4. How can I download or order the data?

Who wrote the metadata?

Dates:
Last modified: 13-May-2005
Metadata author:
VeeAnn A. Cross
U.S. Geological Survey
Marine Geologist
384 Woods Hole Rd.
Woods Hole, MA 02543-1598

(508) 548-8700 x2251 (voice)
(508) 457-2310 (FAX)
vatnipp@usgs.gov

Metadata standard:
FGDC Content Standards for Digital Geospatial Metadata (FGDC-STD-001-1998)
Metadata extensions used:

Generated by mp version 2.8.6 on Fri May 13 13:50:02 2005