The DRG Tools Extension:
The purpose of this extension is to provide basic utilities for use with Digital Raster Graphic (DRG) images created by the Teale Data Center (Teale), the Tennessee Valley Authority (TVA), and the United States Geological Survey (USGS). The extension facilitates batch processing of multiple DRG images, including edgematching, color toggling, and feature isolation. For example, color normalized features (contours, water, etc.) in the images can be isolated and used as overlays with other GIS data. The extension supports DRG images as image themes or image catalogs.
Notes:
The extension will work with most DRG images created by Teale, TVA, and the USGS. Some DRG images with non-standard colors may not be supported.
The addition of the DRG-Tools menu to the view interface is the only change made by the extension to the ArcView environment. For more detailed explanations of menu item functions, highlight each menu item and read the help line at the bottom of the ArcView application window.
The extension works best with views having white (default) backgrounds.
In order to avoid impacting non-DRG themes, the extension will search for and only work on image themes having certain properties that are unique to Teale, TVA, and USGS DRG images. Specifically, colormap index numbers 17, 100, and 255 are examined for each image. If the colors for these index numbers are modified from their original settings, the DRG image will not be recognized. If the extension impacts a non-DRG theme, activate (highlight) the DRG themes of interest and choose to process only the active DRG themes when prompted during certain menu options.
Caution should be taken when altering the original appearances of DRG images. Some image feature colors may not be uniform across all images. The author of this extension is not responsible for any misinterpretations of DRG images caused by use of extension utilities.
The DRG-Tools extension is in the public domain and may be freely redistributed.
Extension Author:
Will Patterson
California Department of Fish and Game
wpatters@dfg.ca.gov
(916) 323-1484
For additional information regarding this Web page, contact Deb Southworth Green , in the Division of Information Technology Management, at Deb_Green@fws.gov
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Keywords=GIS, data, PLGR, elevation
Last Modified January 08, 2001 10:32 AM