A digital raster graphic (DRG) is a

digital image A digital image is an image composed of picture elements, also known as pixels, each with '' finite'', '' discrete quantities'' of numeric representation for its intensity or gray level that is an output from its two-dimensional functions f ...

resulting from scanning a paper

USGS The United States Geological Survey (USGS), founded as the Geological Survey, is an government agency, agency of the United States Department of the Interior, U.S. Department of the Interior whose work spans the disciplines of biology, geograp ...

topographic map In modern mapping, a topographic map or topographic sheet is a type of map characterized by large- scale detail and quantitative representation of relief features, usually using contour lines (connecting points of equal elevation), but histori ...

for use on a computer. DRGs created by USGS are typically scanned at 250 dpi and saved as a

TIFF Tag Image File Format or Tagged Image File Format, commonly known by the abbreviations TIFF or TIF, is an image file format for storing raster graphics images, popular among graphic artists, the publishing industry, and photographers. TIFF is w ...

. The raster image usually includes the original border information, referred to as the "map collar". The map file is UTM projected and georeferenced to the surface of the Earth. DRG's are regularly used in GIS applications. DRGs were first produced in 1995.

External links

* Libre Map Project *
All 50 States USGS Topographic Maps on the Internet Archive
*
USGS Topographic Maps of ALL 50 States
*

Sites *
Digital Raster Graphics
*
Earth Explorer (GeoTIFFs)
*
Map Locator (GeoPDFs)

* Pennsylvania Spatial Data Access sites *
Digital Raster Graphics for PA (free)
*
Digital raster graphics without collar info for PA (free)
* tp://www.pasda.psu.edu/pub/pasda/other_states/wv/drg24k FTP site, DRGs for West Virginia (free)* tp://www.pasda.psu.edu/pub/pasda/other_states/ny/drg24k FTP site, DRGs for New York (free)* tp://www.pasda.psu.edu/pub/pasda/other_states/va/drg24k FTP site, DRGs for Virginia (free)* tp://www.pasda.psu.edu/pub/pasda/other_states/md/drg24k FTP site, DRGs for Maryland (free)* tp://www.pasda.psu.edu/pub/pasda/other_states/dc/drg24k FTP site, DRGs for Washington DC (free)* tp://www.pasda.psu.edu/pub/pasda/other_states/de/drg24k FTP site, DRGs for Delaware (free)* tp://www.pasda.psu.edu/pub/pasda/other_states/nc/drg24k FTP site, DRGs for North Carolina (free)* Texas Natural Resources Information System *
DRGs without collars organized by county
Cartography GIS raster file formats United States Geological Survey {{Cartography-stub

See also

External links