Digital Raster Graphics
Digital Raster Graphics (DRGs) are scanned, digitized and georeferenced USGS topographic maps at 1:24,000, 1:100,00 and 1:250,000 scale. DRGs are in TIFF format (using the GeoTIFF specifications) and are scanned at a minimum resolution of 250 dots per inch. The digital image is georeferenced to the true ground coordinates of the 2.5-minute grid ticks and projected to the Universal Transverse Mercator (UTM) for projection consistency with USGS DOQs and DLGs. The datum of the source materials is preserved in the DRG. If scanned at a finer resolution, the image is resampled to 250 dpi. The image is converted to an 8-bit color image in a compressed TIFF file. Color values are standard between DRG quadrangles. The USGS uses up to 13 colors on each DRG. Color values are contained in each TIFF file.
DRGs are only images of topographic maps. If you need GIS or CAD data of features that are typically depicted on topo maps, then the sources will vary:
- Elevation Data and Contours
- Streets, jurisdictional boundaries, and other useful data are often available from local GIS offices.
- Building footprints, landmarks, utility right-of-ways, and other features, if not available from local GIS sources, are more difficult to find. Contact Data Services for assistance.
For printed hardcopy topographic maps, see our USGS Maps page.
Digital Raster Graphics are available nearly nationwide from many different sources and in many different formats. The following options below focus primarily on availability for DRG's that cover North Carolina.
(For North Carolina, you can look up look up quad names by county here.)
GeoPDF Topographic Maps
The USGS began in 2009 releasing a new mass produced topo map online in digital form only. These maps may be downloaded in GeoPDF format at no cost. The GeoPDF can be read by Adobe Acrobe Reader as a standard PDF. If you install the GeoPDF toolbar for Acrobat Reader from TerraGo, you'll have expanded capabilities with the maps.
To access the maps, go to http://store.usgs.gov" and click "Map Locator..." From there, follow the STEPS given for finding your map(s) of interest.
As of 2010, the new maps are produced using NAIP ortho imagery as a background, NED data for contours, and other national datasets. All areas of North Carolina are complete, except areas around National Forests and Military Bases (see graphic at right), which will be completed in the coming months.
Revised DRGs, 1998-2005
Through a collaborative jointly funded program between the North Carolina Geological Survey (NCGS) and the U.S. Geological Survey, 182 DRGs of North Carolina were revised between 1998 and December 2005.
These files, in TIF format with corresponding world files, may be downloaded from the Geodata server at ftp://gisdata.lib.ncsu.edu/drg/nc_new/. To determine the names of the files you want to download, you'll have to use the documentation table which lists all the revised quadrangles and their file names. All the latest maps are in the Year1rasters folder. Maps in the Year2rasters folder have been supersceeded by Year1rasters maps.
Non-NCSU affiliated users should contact the North Carolina Geologic Survey for information on obtaining these DRGs and maps. They may also be downloaded in GeoPDF format from the USGS Store (discussed below).
NCDOT clipped, projected DRG's
Thanks to NC DOT, DRG's are available to NCSU affiliates as clipped (for seamless tiling) TIF files projected into State Plane 1983/meters (or feet). By "clipped," this means that the white collar around each map containing legends, map names, coordinate system reference points, and other such information has been clipped off. Access these images from the Geodata Server at: ftp://gisdata.lib.ncsu.edu/drg/spclipped/. Data are organized in folders named after the 1:250,000 quadrangle in which they are located.
Data Streaming into GIS Software and Explorer Software
Since DRG's are raster images, streaming the data into your GIS software from remote servers works well. See the Libraries'Web Mapping and Feature Services website for more information, connection instructions, and link for streaming only North Carolina DRGs within both GIS software and as simply as in a web browser.
Streaming topo images into software such as Google Earth and ArcGIS Explorer is relatively simple. Links and specific sources rapidly change, so it's recommend to search Google for files and instructions.
ArcGIS Online provides Topographic Map layers that can be added to ArcGIS and ArcGIS Explorer.
Web-based Viewing, Download, and Purchase Options
The USGS Store has a "Map Locator" which allows selection and download of GeoPDF topographic maps, as well as options to purchase maps. GeoPDF maps are viewable in Adobe Acrobat Reader. If you install the GeoPDF Toolbar, you'll get additional functions (measure distances, locate coordinates, add GPS routes). The most recent topographic maps, including Revised maps discussed above, and maps from the past several decades, are available from the Map Locator.
You may download DRGs as TIFF and TFW (world files) for anywhere in the USA from Libre Map Project. This interface also allows interactive feature searching so you can decide which DRG you need.
The DENR GIS Interface for Topographic Maps provides interactive access to NC topo maps, and allows for user placement of points and text on the maps.
Commercial DRG Software Products
MapTech Terrain Navigator Pro is a commercial stand-alone application that is available on the D. H. Hill Library GIS Workstations for viewing and extracting DRG's for North Carolina. The CD-ROMs are stored in the GIS Data Cabinet under call number G3701 .A25 2003 .T47. Staff at the Ask Us center can assist you with obtaining the correct CD-ROM and logging into a GIS workstation. With this software, 3-D visualization, custom mapping, DRG TIF file export, and many other options are available.
National Geographic TOPO! Mid-Atlantic USA is a CD-ROM based product that allows viewing and exporting of 1:24,000 DRGs for Delaware, Maryland, Virginia, West Virginia, and Washington D.C. (does not include North Carolina). Seamless viewing and 3D shading of relief features are additional product enhancements.
Sure!MAPS Raster Digital Topographic Maps is a commercial digital topographic map product. This data can be viewed in a scale of choice, clipped to an area of choice (seamlessly tiled without collars), output in a density, projection, and format (Arc/Info, ArcView, MapInfo compatibility) of choice. The CD-ROMs are stored in the GIS Data Cabinet at DH Hill Library under call number G3701 .A25 and the software interface is installed on the GIS Workstations.
The Libraries has Sure!Maps Raster data for the following areas and scales:
- 1:24,000 scale: North Carolina
- 1:100,000 scale: United States
- 1:250,000 scale: United States
Click here to see a map illustrating the regions covered by each Sure!Maps Raster CD for the 1:24K North Carolina data.
DRGs on Other CD-ROMs
The Libraries have received a number of USGS DRG CD-ROM's for the southeastern portion of the country, excluding North Carolina (except for some Tennessee and Georgia border areas). The Federal Depository Library Program ceased delivery of DRG's before the North Carolina release, however North Carolina data has since been released by the NC Geological Survey (see below).
The North Carolina Geological Survey has released DRG data for NC on CD-ROM (see NCGS DRG products page). This data is available in the DH Hill Reference Desk GIS CD Cabinet under call number G3901 .A25. Contact Data Services for more information. For a full list of NCGS DRG products see the CD-ROM List and Map.