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


Two Environmental Systems Research Institute (ESRI) ArcView 3.2 Geographic Information System (GIS) project files, data_sa.apr and data_nosa.apr, reside in the top-level directory of this DVD. All associated GIS files are contained within the data directory. The user must have a copy of ESRI ArcView 3.2 in order to view the project files. Visit the ESRI website ( for information concerning this, and other software.

Each project file contains a startup script which prompts the user for the drive letter of the DVD-ROM drive. This information is needed in order to establish "hotlinks" found within the project file. If the ArcView project file and the data directory are copied to the hard disk - maintaining the original directory hierarchy, then the location entered for the startup script should refer to the directory location of the ArcView project file. If for some reason the directory location is entered incorrectly, then the user can click on the pink button with the yellow CD (image of pink button with yellow CD) to reenter the information.

For those users who do not have ArcView 3.2 or later, the individual GIS data files can still be viewed with a compatible GIS viewer, or a free GIS viewer - ArcExplorer. This GIS data viewer is available from ESRI ( ). Please note that the ArcExplorer software is limited to the Microsoft Windows operating systems and some UNIX operating systems.

These projects use raster image files compressed with Mr. Sid Geospatial Encoder version 1.4. In order to load and view these files, the Mr. Sid Image Support extension must be loaded. This extension will be loaded by default within both project files.

The data_sa.apr utilizes gridded data sets. As such, the Spatial Analyst extension must be loaded in order to view and manipulate these grids. This extension is loaded by default within the data_sa.apr. For users who do not have the Spatial Analyst extension, data_nosa.apr utilizes TIFF or Mr. Sid images of the grid datasets. The necessary extensions will be loaded by default within the project file.

All of the shapefiles are in the Geographic NAD83 coordinate system. Most of the grids and images are available in both the Geographic NAD83 coordinate system, and UTM, Zone 11, NAD83 projection. Within the project files, the data loaded into the project views are all in the Geographic NAD83 coordinate system.

The seismic trackline data presented within the project files are "hotlinked" to HTML files containing the interpreted and uninterpreted JPEG images of the seismic reflection profiles. To view these HTML documents, click on the lightning bolt (image of lightening bolt) within the project tool bar, and click on an individual trackline within an active trackline theme. The user's default WWW browser will be activated to view the document. These HTML documents can also be viewed directly from the data/htmlseis directory. These HTML documents require that the seisimages directory maintain its relative position to the htmlseis directory.

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