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A Digital Raster Graphic (DRG) is a scanned image of a USGS standard series topographic map, including all map collar information.
The image inside the map neat line is geo-referenced to the surface of the earth and fit to the Universal Transverse Mercator (UTM) projection. The horizontal
positional accuracy and datum of the DRG matches the accuracy and datum of the source map. The map is scanned at a minimum resolution of 250 dots per inch and
is printed at MapSport at a resolution of 600 dots per inch which produces a very detailed, accurate reproduction of the original dem topographic.
One note about DRG scans, the scale along the Latitude lines will be reasonably close, however the scale along the longitude lines may less accurate.
Visually you will not be able to discern a problem, however if accurate scaling is important, digital (not scanned) dem data would be more appropriate.
Sportsmen, Hunters, Hikers use the maps to plan appropriate hunting and hiking areas and once in the the field to assist with recognizing
terrain and location, adjusting the days hike or hunt or locating a specific terrain feature. Engineers and surveyors (and landowners) us the topo
maps to locate pipeline and powerline construction, to assist with land management issues and develop water runoff and containment plans. These are
only a sampling of all the ways the topo maps can be used.
Included in MapSport are all DRGs in the USGS standard topographic map series for the United State, USGS web site.
24k - DRGs of the US, Hawaii, and parts of Alaska at 1:24,000 or 1:25,000 scale.
63k - DRGs of Alaska at 1:63,360-scale.
100k - DRGs of the United States at 1:100,000 scale.
250k - DRGs of the United States at 1:250,000 scale.
Also indluded are DRGs for the following non-USGS agencies.
24k - DRGs of California are made by the California Spatial Information Library, CSIL web site.
24k - DRGs of parts of Tennessee and neighboring states are made by the Tennessee Valley Authority, TVA web site.
See the DRG status graphic for approximate
areas of coverage. DRG technical specifications vary slightly for the non-USGS maps.
Additional USGS Links: USGS index system explanation
and USGS map locator tool.
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