Sidescan-sonar Tracklines in the Geographic Coordinate System - Lake Mead 2000

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Frequently anticipated questions:


What does this data set describe?

Title:
Sidescan-sonar Tracklines in the Geographic Coordinate System - Lake Mead 2000
Abstract:
A one-week geophysical survey was conducted in the Las Vegas Bay part of Lake Mead during June 1-6, 2000 to acoustically map the surficial sediments and shallow subsurface geology of this part of the lake. The study was done by researchers from the U.S. Geological Survey, Coastal and Marine Geology Program in Woods Hole, MA and the University of Nevada at Las Vegas. The objective was to map the distribution, volume and acoustic character of sediment that has accumulated on the floor of this part of the lake. The need for systematic mapping of this part of the lake's floor is because pollutants associated with surface and groundwater enter the lake through Las Vegas Wash at the head of Las Vegas Bay. Some of the pollutants transported to the lake by this runoff are deposited with the sediments on the lake floor. Understanding the distribution of sediments in the lake is needed to establish an effective monitoring program. The study built upon a geophysical survey conducted by the USGS and UNLV in 1999 that covered the deeper water parts of Las Vegas Bay and Boulder Basin. This year's survey focussed on the shallow water parts of the head of Las Vegas Bay with particular attention being directed at Las Vegas, Gypsum and Government Washes. Of these three Washes, the most effort was put into surveying Las Vegas Wash. This survey was conducted with an Edgetech DF-1000 sidescan sonar, a Knudsen high-resolution chirp subbottom profiling system, a Garmin fathometer, and P-Code GPS navigation. All data were logged digitally.
  1. How might this data set be cited?
    Twichell, David C., and Cross, VeeAnn A., 2003, Sidescan-sonar Tracklines in the Geographic Coordinate System - Lake Mead 2000: Open-File Report 03-320, 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.

    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, Reston, VA.

    Online Links:

  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -114.874450
    East_Bounding_Coordinate: -114.808870
    North_Bounding_Coordinate: 36.135890
    South_Bounding_Coordinate: 36.114000
  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: vector digital data
  6. How does the data set represent geographic features?
    1. How are geographic features stored in the data set?
      This is a Vector data set. It contains the following vector data types (SDTS terminology):
      • String (26)
    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 0.000001. Longitudes are given to the nearest 0.000001. 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?
    ssnav_00.dbf
    ArcView shapefile attribute table (Source: ESRI)
    FID
    Internal feature number. (Source: ESRI) Sequential unique whole numbers that are automatically generated.
    Shape
    Feature geometry. (Source: ESRI) Coordinates defining the features.
    LINENUM
    A numeric value indicating a line number. Test files collected during the cruise and subsequently used for interpretations are given line numbers in the range of 501-503. This is to differentiate test file 1 from line 1. (Source: VeeAnn A. Cross)
    Range of values
    Minimum:1
    Maximum:503
    FILENAME
    Prefix of the filename assigned to each line of sidescan-sonar data collected. (Source: Kenneth F. Parolski) Character data set
    SWATH
    The total swath that the sidescan-sonar imagery covers (in meters). (Source: VeeAnn A. Cross)
    ValueDefinition
    200m200 meters
    lengthm
    The length of each line segment in meters. (Source: Software computed.)
    Range of values
    Minimum:529
    Maximum:2243

Who produced the data set?

  1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)
    • David C. Twichell
    • VeeAnn A. Cross
  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

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

Why was the data set created?

This ArcView shapefile defines the tracklines along which sidescan sonar data was collected.

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: unknown (process 1 of 8)
    Navigation was acquired by a Hypack navigation system and stored with the Edgetech sidescan sonar data on a QMIPS computer data acquisition system. A unique navigation point was sent to the acquisition system approximately every 10 seconds. Upon extracting the sidescan-sonar data from the acquisition system, the navigation was downsampled to 1 minute intervals.
    Date: unknown (process 2 of 8)
    This 1 minute navigation was then reviewed for errors and sometimes further downsampled to enable the swath of sidescan-sonar imagery to have a smooth track.
    Date: unknown (process 3 of 8)
    This navigation for each line of sidescan data was then combined with all the other lines into an Arc/Info ungenerate format for import into ArcView.
    Date: unknown (process 4 of 8)
    Within ArcView, additional attribute information for each line was added.
    Date: 30-Mar-2017 (process 5 of 8)
    Edits to the metadata were made to fix any errors that MP v 2.9.36 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.). Added online links to the data in the identification section and the distribution section and also a link to the larger work citation. Added ISO 19115 Topic Category keywords. The standard order process section in the Distribution section was incomplete and had to be modified to meet the standard. The information in the quantitative horizontal accuracy assessment was moved to the horizontal positional accuracy report. 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 Road
    Woods Hole, MA

    508-548-8700 x2251 (voice)
    508-457-2310 (FAX)
    vatnipp@usgs.gov
    Date: 20-Jul-2018 (process 6 of 8)
    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 7 of 8)
    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 8 of 8)
    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?
    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 endrocrinology and histology, Las Vegas Wash and Las Vegas and Callville bays of Lake Mead Nevada: Water-Resources Investigations 96-4266, U.S. Geological Survey, Reston, VA.

    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, Reston, VA.

    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, Reston, VA.

    Cross, V.A., and Twichell, D.C., 2003, Archive of Seismic-Reflection Data Collected During USGS Cruise Lake Mead 00027 in Lake Mead - Nevada, 1-6 June, 2000: Open-File Report 03-004, U.S. Geological Survey, Reston, VA.

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

    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, Reston, VA.


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 navigation data were collected with a P-CODE GPS with an assumed accurace of +/- 10 m. Additional error is encountered due to the offset between the sidescan-sonar towfish and the navigation antenna. Furthermore, the navigation was downsampled so that only the most accurate navigation positions are the vertex points of the line. Assumed accuracy 10-20 meters.
  3. How accurate are the heights or depths?
  4. Where are the gaps in the data? What is missing?
    Complete.
  5. How consistent are the relationships among the observations, including topology?
    These lines represent the lines along which sidescan-sonar image data were collected.

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

    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: 08-Sep-2020
Metadata author:
VeeAnn A. Cross
U.S. Geological Survey
Marine Geologist
REQUIRED: The city of the address., REQUIRED: The state or province of the address.

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)

This page is <https://cmgds.marine.usgs.gov/catalog/whcmsc/open_file_report/ofr2003-320/ssnav_00meta.faq.html>
Generated by mp version 2.9.50 on Tue Sep 21 18:20:18 2021