U.S. geological survey standard for digital raster graphics
Author(s)/Corporate Author (s)United Nations. Economic Commission for Africa;
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A digital raster graphic (DRG) is a raster image of a published map. The U.S. Geological Survey plans to produce DRG's of its standard topographic map series through contracts with the private sector and through partnerships with State agencies. DRG's are made by scanning published paper maps on high-resolution scanners. The raster image is geo referenced and fit to the UTM grid. Colors are standardized to remove scanner dependencies and artifacts. The final data set is about 10 megabytes in Tagged Image File Format (TIFF) with pack bit compression. DRG's can be easily combined with other digital cartographic products, such as digital elevation models and digital ortho photo quads. Using DRG's and derivative products as source material makes vector data collection and revision faster, cheaper, and more accurate than traditional methods. DRG's provide a spatially accurate, visually appealing backdrop for other geographic data. A DRG combined with a digital orthophotoquad image can be used for monoscopic vector collection and revision. The combined image significantly reduces total collection and revision times. DRG's can provide inexpensive, consistent base data for the entire country.