Reformatted Hypack Navigation from Lake Mead - 2000

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?
• 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?

Title: Reformatted Hypack Navigation from Lake Mead - 2000

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.

1. How should this data set be cited?

   Cross, VeeAnn A. , and Twichell, David C. , 2003, Reformatted Hypack Navigation from Lake Mead - 2000:.

   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.

2. What geographic area does the data set cover?

   West_Bounding_Coordinate: -114.876820

   East_Bounding_Coordinate: -114.737250

   North_Bounding_Coordinate: 36.135920

   South_Bounding_Coordinate: 36.081650

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?

6. How does the data set represent geographic features?
   1. How are geographic features stored in the data set?

      This is a Point data set.

   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 0.0001. Longitudes are given to the nearest 0.0001. 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?

   Entity_and_Attribute_Overview:

   This text file has a total of 4 columns. Column 1: Date and time (GMT) as julian day(xxx):hour(xx):minute(xx):second(xx) Column 2: Longitude (decimal degrees) Column 3: Latitude (decimal degrees) Column 4: Depth from fathometer (in meters - becasue the number is negative, subtract 1 meter to account for draft)

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

2. Who also contributed to the data set?

3. To whom should users address questions about the data?

   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
   

This file represents the raw navigation acquired on the cruise, including the fathometer data (point bathymetry data) collected on the cruise. WARNING: These data have not been checked for errors.

1. From what previous works were the data drawn?

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

   (process 1 of 2)

   After each survey day, the navigation acquired with the Hypack software was reformatted into a 4 column format.

   (process 2 of 2)

   At the end of the cruise, all of this navigation was combined into one ASCII text file.

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?

   This file encompasses all of the navigation logged with the Hypack navigation system.

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

   This navigation was collected with the same acquisition system, therefore internally consistent.

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)

   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
   

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?

Dates:

Last modified: 04-Feb-2003

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:

• <http://www.esri.com/metadata/esriprof80.html>