Enhanced TIFF Sidescan-Sonar Mosaic of Las Vegas Wash - Lake Mead, Nevada: Geographic Coordinates

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Frequently-anticipated questions:

What does this data set describe?

Title:
Enhanced TIFF Sidescan-Sonar Mosaic of Las Vegas Wash - Lake Mead, Nevada: Geographic Coordinates
Abstract:
Lake Mead is a large interstate reservoir located in the Mojave Desert of southeastern Nevada and northwestern Arizona. It was impounded in 1935 by the construction of Hoover Dam and is one of a series of multi-purpose reservoirs on the Colorado River. The lake extends 183 km from the mouth of the Grand Canyon to Black Canyon, the site of Hoover Dam, and provides water for residential, commercial, industrial, recreational, and other non-agricultural users in communities across the southwestern United States. Extensive research has been conducted on Lake Mead, but a majority of the studies have involved determining levels of anthropogenic contaminants such as synthetic organic compounds, heavy metals and dissolved ions, furans/dioxins, and nutrient loading in lake water, sediment, and biota (Preissler, et al., 1998; Bevans et al, 1996; Bevans et al., 1998; Covay and Leiker, 1998; LaBounty and Horn, 1997; Paulson, 1981). By contrast, little work has focused on the sediments in the lake and the processes of deposition (Gould, 1951). To address these questions, sidescan-sonar imagery and high-resolution seismic-reflection profiles were collected throughout Lake Mead by the USGS in cooperation with researchers from University of Nevada Las Vegas (UNLV). These data allow a detailed mapping of the surficial geology and the distribution and thickness of sediment that has accumulated in the lake since the completion of Hoover Dam. Results indicate that the accumulation of post-impoundment sediment is primarily restricted to former river and stream beds that are now submerged below the lake while the margins of the lake appear to be devoid of post-impoundment sediment. The sediment cover along the original Colorado River bed is continuous and is typically greater than 10 m thick through much of its length. Sediment thickness in some areas exceeds 35 m while the smaller tributary valleys typically are filled with less than 4 m of sediment. Away from the river beds that are now covered with post-impoundment sediment, pre-impoundment alluvial deposits and rock outcrops are still exposed on the lake floor.
Supplemental_Information:
This previously published dataset is provided as a courtesy in Open-File Report 1150 "Surficial Geology of the Floor of Lake Mead (Arizona and Nevada) as Defined by Sidescan-sonar Imagery, Lake Floor Topography and Post-impoundment Sediment Thickness", available online: <https://pubs.usgs.gov/of/2009/1150/>. Improvements have been made to this metadata file even though the originally published data have not been modified.
  1. How should this data set be cited?

    Twichell, David C. , and Cross, VeeAnn A. , 2003, Enhanced TIFF Sidescan-Sonar Mosaic of Las Vegas Wash - Lake Mead, Nevada: Geographic Coordinates:.

    Online Links:

    This is part of the following larger work.

    Twichell, David C. , Cross, VeeAnn A. , and Belew, Stephen D. , 2003, Mapping the floor of Lake Mead (Nevada and Arizona): Preliminary discussion and GIS data release: Open-File Report 03-320, U.S. Geological Survey, Woods Hole Field Center, Woods Hole, MA.

    Online Links:

  2. What geographic area does the data set cover?

    West_Bounding_Coordinate: -114.877684
    East_Bounding_Coordinate: -114.805632
    North_Bounding_Coordinate: 36.139662
    South_Bounding_Coordinate: 36.109849

  3. What does it look like?

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

    Beginning_Date: 01-Jun-2000
    Ending_Date: 06-Jun-2000
    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 3308 x 6468 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. Latitudes are given to the nearest 0.000009. Longitudes are given to the nearest 0.000011. Latitude and longitude values are specified in Decimal degrees.

      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:
    The pixel value represents the DN return value of the sidescan-sonar system. A high value (ie 254) indicates a highly reflective lake floor surface, while a low value (ie 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 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 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?

    Date: Jun-2000 (process 1 of 4)
    Sidescan sonar imagery was collected using an Edgetech DF1000 sidescan sonar system and logged to a Triton QMIPS data logging computer. All of the data were collected at a 200m 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).

    Person who carried out this activity:

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

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

    Data sources used in this process:
    • 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, p. 54-59.

    Date: Jun-2000 (process 2 of 4)
    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:

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

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

    Data sources used in this process:
    • Paskevich, V.F., 1996, MAPIT: An improved method for mapping digital sidescan sonar data using the Woods Hole Image Processing System (WHIPS) software: U.S. Geological Survey Open-File Report 96-281, 73p.

    Date: Jun-2000 (process 3 of 4)
    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). A root stretch from 0-254 was applied to the sidescan image. The imagery portion was then cut out and written to a PCI channel with a white background. By doing this, within ArcView the user can turn the 255 pixel value to transparent and only display the actual sidescan imagery. This enhanced image was then exported from PCI as a TIFF image with an associated world file for georeferencing purposes.

    Person who carried out this activity:

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

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

    Data sources used in this process:
    • Paskevich, V.F., 1992, Digital mapping of sidescan sonar data with the Woods Hole Image Processing System software: U.S. Geological Survey Open-File Report 92-536, 87p.

    (process 4 of 4)
    The UTM projected image was the reprojected to Geographic coordinates using BlueMarble's Geographic Transformer software. Transform parameters used a resolution of 1m/pixel and a central latitude of 36N.

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

    Bevans, H.E., Goodbred, S.L., Miesner, J.F., Watkins, S.A., Gross, T.S., Denslow, N.D., and Choeb, T., 1996, Synthetic organic compounds and carp endocrinology and histology, Las Vegas Wash and Las Vegas and Callville bays of Lake Mead Nevada: Water-Resources Investigations 96-4266, U.S. Geological Survey.

    Bevans, H.E., Lico, M.S., and Lawrence, S.J., 1998, Water quality in the Las Vegas Valley area and the Carson and Truckee River basins, Nevada and California, 1992-1996: Circular 1170, U.S. Geological Survey.

    Couvay, K.J., and Leiker, T.J., 1998, Synthetic organic compounds in water and bottom sediment from streams, detention basins, and sewage-treatment plant outfalls in Las Vegas Valley, Nevada, 1997: Open-File Report 98-633, U.S. Geological Survey.

    Gould, H.R., 1951, Some quantitative aspects of Lake Mead turbidity currents: SEPM Special Publication No. 2, Society of Economic Paleontologists and Mineralogists.

    LaBounty, J.F., and Horn, M.J., 1997, The influence of drainage from the Las Vegas Valley on the limnology of Boulder Basin, Lake Mead, Arizona-Nevada: Journal of Lake and Reservoir Management v. 13.

    Paulson, L.J., 1981, Nutrient management with hydroelectric dams on the Colorado River: Technical Report #8, Lake Mead Limnological Research Center, Department of Biological Sciences, University of Nevada, Las Vegas, Nevada.

    Preissler, A.M., Roach, G.A., Thomas, K.A., and Wilson, J.W., 1998, Water resources data, Nevada, water year 1998: Water Resources Data Nevada NV-98-1, 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 P-CODE GPS. The towfish was deployed at approximately the same depth each day, with little variation during the course of the survey. Due to the shipboard configuration, the navigation antennae was placed at the approximate layback position of the towfish, therefore range to fish errors are assumed to be negligible.

  3. How accurate are the heights or depths?

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

    All imagery necessary to map the lake floor of interest in this particular study was used.

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

    All of these data were collected with the same sidescan-sonar towfish - the Edgetech DF1000. All data were collected as 16-bit, 200m swath, 1024 pixels/side.

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?

    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 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?

    The user must be capable of uncompressing the WinZip file. In addition, to view the TIFF image spatially, the user must have software that is capable of reading the GeoTIFF header information, or alternatively, read the TIFF world file spatial reference information.

Who wrote the metadata?

Dates:
Last modified: 04-Aug-2009
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 2.9.6 on Tue Aug 04 15:07:08 2009