# MOSAIC_COMP – Composite Sidescan-Sonar Mosaic collected by the U.S. Geological Survey offshore of the Grand Strand, SC (1999 – 2003) (Compressed - MrSID)

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#### Frequently-anticipated questions:

- What does this data set describe?
  1. How should this data set be cited?
  2. What geographic area does the data set cover?
  3. What does it look like?
  4. Does the data set describe conditions during a particular time period?
  5. What is the general form of this data set?
  6. How does the data set represent geographic features?
  7. How does the data set describe geographic features?
- Who produced the data set?
  1. Who are the originators of the data set?
  2. Who also contributed to the data set?
  3. To whom should users address questions about the data?
- Why was the data set created?
- How was the data set created?
  1. From what previous works were the data drawn?
  2. How were the data generated, processed, and modified?
  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?
  2. How accurate are the geographic locations?
  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 data, including topology?
- How can someone get a copy of the data set?
  1. Are there legal restrictions on access or use of the data?
  2. Who distributes the data?
  3. What's the catalog number I need to order this data set?
  4. What legal disclaimers am I supposed to read?
  5. How can I download or order the data?
- Who wrote the metadata?

### What does this data set describe?

Title:
  MOSAIC_COMP – Composite Sidescan-Sonar Mosaic collected by the U.S. Geological Survey offshore of the Grand Strand, SC (1999 – 2003) (Compressed - MrSID)
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, MOSAIC_COMP – Composite Sidescan-Sonar Mosaic collected by the U.S. Geological Survey offshore of the Grand Strand, SC (1999 – 2003) (Compressed - MrSID): Open-File Report 2005-1346, U.S. Geological Survey, Coastal and Marine Geology Program, Woods Hole Science Center, Woods Hole, MA.

   > Online Links:

   > - <http://pubs.usgs.gov/of/2005/1346/ArcGIS/Mosaic/mosaic_sid.zip>

   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, Edition 1.0 Series_Information Series_Name: U.S. Geological Survey, Coastal and Marine Geology Program, Woods Hole Science Center, Woods Hole, MA.

   > Online Links:

   > - <http://pubs.usgs.gov/of/2005/1346/>

2. What geographic area does the data set cover?

   West_Bounding_Coordinate: -79.177122
   East_Bounding_Coordinate: -78.492052
   North_Bounding_Coordinate: 33.876672
   South_Bounding_Coordinate: 33.143971

3. What does it look like?

   <http://pubs.usgs.gov/of/2005/1346/images/mosaic.jpg> (JPEG)
     grey-scale image of sidescan-sonar mosaic

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: 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 20000 x 15500 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: 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 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?

   `Band_1`
     Sidescan-Sonar image stored in MrSid format (Source: ESRI)

     `ObjectID`
       Internal feature number. (Source: ESRI)

       Sequential unique whole numbers that are automatically generated.

     `Value`
       pixel values in the range of 0-255; 0 represents low backscatter; 255 represents high backscatter (Source: USGS)

       Range of values
       Minimum: | 0
       Maximum: | 255
       Units: | digital number
       Resolution: | 1

     `Count`
       pixel count (Source: USGS)

       Range of values
       Minimum: | 0
       Maximum: | 249232064
       Units: | unrepresented
       Resolution: | 1

   Entity_and_Attribute_Overview:
     There are no attributes associated with a MrSid image. 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).
   Entity_and_Attribute_Detail_Citation: USGS

### 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?

   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 the sidescan-sonar imagery collected offshore of the Grand Strand, SC 1999 - 2003. These data are used in conjunction with surficial sediment analyses to define the sediment distribution within the survey area.

### 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: 1999 (process 1 of 2)
     The sidescan-sonar data were acquired with a Benthos (Datasonics) SIS 1000 CHIRP sonar and Edgetech DF-1000 dual-frequency sonar systems. The SIS-100 operates in a frequency range of 100 - 120 kHz; the DF-1000 operates at 100 and 500 kHz. The sidescan-sonar imagery offshore of the Grand Strand is comprised of data acquired on six geophysical cruises operated by the USGS during 1999 - 2003.
     All sidescan-sonar data were logged digitally at a sample rate resulting in a 0.18-m pixel size in the across-track direction and approximately 0.14-m in the along-track direction following the methodology outlined in Danforth and others (1991). A median filtering routine (Malinverno and others, 1990) was applied to the sidescan-sonar data to remove speckle noise, resulting in a 0.73-m pixel size. The data for each survey were further processed and digitally mosaicked using PCI Geomatica Software and procedures described in Danforth and others (1991), Danforth (1997), and Paskevich (1992) resulting in an enhanced, geographically correct, sidescan-sonar mosaic with 2 meters/pixel resolution. The composite mosaic was exported as a TIFF image, with an associated ESRI world file.

     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:
     - Danforth, W.W., 1997, Xsonar/ShowImage: A complete system for rapid sidescan-sonar processing and display: U.S. Geological Survey Open File Report 97-686, 77 p.
     - 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, Vol 1, p.54-59.
     - Malinverno, A., Edwards, M, and Ryan, W.B.F, 1990, Processing of SeaMARC swath sonar data: IEEE, Journal of Ocean Engineering, v.15, p. 14-23.
     - Paskevich, V., 1992, Digital mapping of sidescan-sonar data with the Woods Hole Image Processing System software: U.S. Geological Survey Open-File Report 92-536, 87.p

   Date: 2003 (process 2 of 2)
     The sidescan-sonar mosaic was compressed using MrSid. A compression of 20x was used.

     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

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 measure the acoustic reflectivity of the seafloor. These values (Digital Number (DN)) are a relative measure of reflectivity within the study area and are internally consistent.

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). Slant-range distance is recorded between the sidescan-sonar tow vehicle and a sidemount rigged with an acoustic transponder. Offset between the sidemount and GPS antennae is measured. Basic trigonomic calculations use the slant-range offset to calculate a 'fish' (tow-vehicle) navigation. An assumption in these calculations is that the tow-vehicle is traveling directly behind the vessel; movement to port or starboard is not accounted for within 'fish' navigation. Thus, the horizontal accuracy of the sidescan-sonar tow-vehicle is 10 meters.

3. How accurate are the heights or depths?

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

   No additional checks were made for topologic consistency.

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

   These are raster data; all sidescan-sonar data collected during USGS field efforts offshore of Myrtle Beach, SC 1999 – 2003 are included. Processing removed any spurious 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:
> >   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?

   - Availability in digital form:

     Data format: | File contains the sidescan-sonar imagery collected offshore of the Grand Strand. SC in format MrSID (version ArcGIS 9.0) MrSID Image compression Size: 9.428
     Network links: | <http://pubs.usgs.gov/of/2005/1346/ArcGIS/Mosaic/mosaic_sid.zip>
     Media you can order: | DVD-ROM (Density 4.75 Gbytes) (format UDF)

   - Cost to order the data: none

5. What hardware or software do I need in order to use the data set?

   > This image is available as a compressed MrSID 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 MrSID image.

### Who wrote the metadata?

Dates:
  Last modified: 15-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)

Generated by `mp` version 2.9.2 on Tue Mar 06 15:56:09 2007