Mapping the floor of Lake Mead (Nevada and Arizona): Preliminary discussion and GIS data release, USGS Open-File Report 03-320

DVD DIRECTORY STRUCTURE

Top level directory:

disc_acc.htm - This file is the disclaimer for this DVD and describes USGS accessibility requirements.

index.htm - This file is intended to be the starting point for the DVD-ROM access. It is written in the Hypertext Markup Language utilized by the World Wide Web (WWW) project and must be opened with a WWW browser. Once opened, the user may browse the DVD-ROM's contents as they would browse pages from the WWW.

readme.txt - ASCII text file containing a description of this DVD-ROM. This file may be viewed or printed with any system program capable of opening ASCII text files.

data_sa.apr - ArcView project file created with ArcView 3.2a on a Windows2000 computer. This ArcView project contains grids and requires the ArcView extension Spatial Analyst.

data_nosa.apr - ArcView project file created with ArcView 3.2a on a Windows2000 computer. This ArcView project uses TIFF or Mr. Sid images with associated world files instead of ESRI formatted grids. This removes the dependency on the Spatial Analyst extension such that any user with ArcView version 3.2 or a later version can view the project.

Directories:

Directory data - What follows is a brief description of the data contained in the underlying directories. For a more complete description of the data, refer to the metadata associated with each data file. This directory contains the following subdirectories:

• bounds - contains basic boundary files of the study area including the lake bounds, extent of post-impoundment sediment, and the paleo-thalweg of the Colorado River.
• doq - contains mosaicked DOQ images of the study area downsampled to 4m/pixel. These images are available in Mr. Sid image format, in both geographic and UTM, Zone 11, NAD83 coordinate systems.
• htmlseis - html documents containing the uninterpreted and interpreted seismic reflection profiles for all the seismic reflection profiles collected as a part of this study. The data are separated by collection year in the following subdirectories: 1999, 2000, and 2001.
• isopach - contains the isopach (sediment thickness) data from Lake Mead in both grid and TIFF image format.
• nav - contains navigation data separated by year of collection in the following subdirectories: 1999, 2000, and 2001.
• pdflogs - contains the PDF versions of the field logbooks maintained during each year of data collection. The logbooks are stored in the following subdirectories based on year of collection: 1999, 2000, and 2001.
• seisimages - contains JPEG images of all the seismic reflection profiles (both uninterpreted and interpreted) collected as a part of this study. The data are stored in the following subdirectories based on year of collection: 1999, 2000, and 2001.
• sscanimgs - contains sidescan-sonar mosaics. The initial directory division is based upon projection: geographic or UTM, Zone 11, NAD83. Each of these directories contains enhanced and unenhanced mosaics in Mr. Sid and TIFF formats. The mosaics are divided into 5 areas so that the final mosaic is not unmanageably large. Las Vegas Wash is mapped at 1 m/pixel, while the remaining mosaics are 2 m/pixel. In the eastern portion of the lake (east of Boulder Canyon see Fig. 1), one set of enhanced images (only available in the UTM projection) attempts to tone-match the mosaics. These files reside in the data/sscanimgs/utm11/dctenh directory.
• surfaces - contains grids and images (TIFF and Mr. Sid formats) representing the present day surface of the study area. These data combine the on land DEM with the lakefloor bathymetry. The data are stored in the following subdirectories: utm11 and geographic.

Directory htmldocs: contains the HTML pages accessed within this Open-File Report (excluding the seismic HTML pages accessible from the ArcView projects). This directory contains the following subdirectories:

• icons - contains all the images files and icons utilized in constructing the Open-File Report HTML pages.
• pdf - contains the PDF version of the Open-File Report. This PDF document does not maintain all the links found on the GIS metadata and data catalog page.

Directory metadata: contains the HTML and ASCII text versions of the metadata files for all the data contained in this Open-File Report. This directory has the following subdirectories: bounds, doq, htmlseis, isopach, nav, pdflogs, seisimages, sscanimgs, and surfaces.

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