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), formerly simply known as the Geological Survey, is a scientific agency of the United States government. The scientists of the USGS study the landscape of the United States, its natural resources, ...

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, abbreviated TIFF or TIF, is an image file format for storing raster graphics images, popular among graphic artists, the publishing industry, and photographers. TIFF is widely supported by scanning, faxing, word processin ...

. The raster image usually includes the original border information, referred to as the "map collar". The map file is

UTM UTM may refer to: Computing * Unified threat management, an approach to network security * Universal Turing machine, a theoretical computer * Urchin Tracking Module, a Web analytics package that served as the base for Google Analytics * Usabil ...

projected and

georeference Georeferencing means that the internal coordinate system of a map or aerial photo image can be related to a geographic coordinate system. The relevant coordinate transforms are typically stored within the image file (GeoPDF and GeoTIFF are examples) ...

d 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 Pennsylvania Spatial Data Access (PASDA) is Pennsylvania's official public access geospatial information clearinghouse. PASDA serves as Pennsylvania's node on the National Spatial Data Infrastructure (NSDI). PASDA is a cooperative effort of the Pen ...

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 The Texas Natural Resources Information System (TNRIS) is the principal state archive in Texas for natural resources data. TNRIS provides a central access point for Texas Natural Resources data, census data, digital and paper maps, and informatio ...

*
DRGs without collars organized by county
Cartography GIS file formats United States Geological Survey {{Cartography-stub

See also

External links