Sidescan-Sonar mosaic of Lake Mohave, MrSid format : UTM, Zone 11, NAD83 Projection

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Frequently-anticipated questions:

What does this data set describe?

Title:
Sidescan-Sonar mosaic of Lake Mohave, MrSid format : UTM, Zone 11, NAD83 Projection
Abstract:
Lake Mohave is one of several multi-purpose reservoirs that have been constructed on the Colorado River. The lake was formed upon completion of the Davis Dam in 1953. No mapping of the floor of the lake had been conducted since completion of the Davis Dam. The U.S. Geological Survey, in cooperation with researchers from the University of Nevada Las Vegas, completed a geophysical survey of this lake in April 2002. The survey included collection of sidescan sonar imagery of nearly the entire lake floor, and high-resolution seismic-reflection profiles along widely spaced lines throughout the lake. The detailed mapping of the lake floor was used to determine the amount of sediment that had accumulated in the lake since impoundment, its distribution, and the processes of deposition.
  1. How should this data set be cited?

    Foster, David S. , and Cross, VeeAnn A. , 2005, Sidescan-Sonar mosaic of Lake Mohave, MrSid format : UTM, Zone 11, NAD83 Projection:.

    Online Links:

    This is part of the following larger work.

    Cross, VeeAnn A. , Foster, David S. , and Twichell, David C. , 2005, Lake Mohave Geophysical Survey 2002: GIS Data Release: Open-File Report 2004-1247, U.S. Geological Survey, Woods Hole Science Center, Woods Hole, MA.

    Online Links:

  2. What geographic area does the data set cover?

    West_Bounding_Coordinate: -114.733561
    East_Bounding_Coordinate: -114.549418
    North_Bounding_Coordinate: 35.870509
    South_Bounding_Coordinate: 35.199202

  3. What does it look like?

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

    Beginning_Date: 18-Apr-2002
    Ending_Date: 25-Apr-2002
    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 37079 x 7466 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: 11
      Transverse_Mercator:
      Scale_Factor_at_Central_Meridian: 0.999600
      Longitude_of_Central_Meridian: -117.000000
      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 2.000000
      Ordinates (y-coordinates) are specified to the nearest 2.000000
      Planar coordinates are specified in meters

      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

    Count

    Entity_and_Attribute_Overview:
    The pixel value represents the DN return value of the sidescan-sonar system. A high value (i.e. 255) indicates a highly reflective lake floor surface, while a low value (i.e. 0) indicates low reflectance.

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 S. Foster
    U.S. Geological Survey
    Geologist
    384 Woods Hole Rd.
    Woods Hole, MA 02543-1598

    (508) 548-8700 x2271 (voice)
    (508) 457-2310 (FAX)
    dfoster@usgs.gov

Why was the data set created?

This sidescan-sonar imagery is used to map the morphology of the lake floor and determine the extent of sediment distribution on the lake floor.

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 Edgetech DF1000 sidescan sonar system and logged to a Triton QMIPS data logging computer. The data were collected at a 150m, 200m, 400m, or 600m swath, 1024 pixels/side, 16-bit. 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).

    (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).

    (process 3 of 7)
    The imagery was mapped into its proper geographic location using the XSonar software. Individual sidescan swaths were mapped with each pixel geographically positioned at a resolution of 2 m/pixel.

    (process 4 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 (1996). The imagery portion was then cut out and written to a PCI channel with a white background. A LUT was applied to the imagery such that the image contains values 0-254. Because the background is 255, that color can be made transparent when viewing in a GIS.

    (process 5 of 7)
    The image was then exported from PCI as a geotiff image with an associated world file.

    (process 6 of 7)
    Because the original mosaicking was done in UTM, Zone 11, WGS84, the resulting TIFF image was then reprojected to the NAD83 datum using BlueMarble Geographic Transformer, version 5.0. This ensures that all the GIS data are in the same datum.

    (process 7 of 7)
    This TIFF image was then compressed using LizardTech's MrSide Geospatial Encoder version 1.4.

  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.

    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?

  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 S. Foster
    U.S. Geological Survey
    Geologist
    384 Woods Hole Rd.
    Woods Hole, MA 02543-1598

    (508) 548-8700 x2271 (voice)
    (508) 457-2310 (FAX)
    dfoster@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 publication 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: 28-Sep-2004
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 2.8.12 on Tue Sep 28 15:51:24 2004