California Department of Fish and Wildlife

Related GIS Links

 

Department of Fish & Wildlife
Biogeographic Data Branch
1807 13th Street, Suite 202
Sacramento, CA 95811
(916) 322-2493 • Email BDB

Digital Raster Graphics

 

California Department of Fish and Game (DFG) — Spatial Data Resources

Scanned USGS Topographic Maps (Digital Raster Graphics - "DRGs")

This page reviews options for acquiring digital versions of USGS topographic maps. A Digital Raster Graphic or "DRG" is a georeferenced digital image of a USGS topographic map. DRGs are freely sharable and can be viewed with many GIS and imaging software programs.

Statewide sets of DRG images are available in 3 scales (levels of detail) based on the source USGS topographic maps. The images are available untrimmed (with map collars) or trimmed (map collars removed). Untrimmed DRG images contain all the map collar information in the image (such as tic marks, map dates, and documentation). Trimmed DRG images provide seamless map display for cartographic purposes. Mosaics of the trimmed DRG products are also available, providing "blocks" of imagery that cover many topo maps.

DRGs are georeferenced to various projections and horizontal datums for use in GIS programs. In California, DRGs are typically provided in the California Teale Albers projection. For the rest of the United States, they are usually in the Universal Transverse Mercator (UTM) projection. The horizontal datum used by DRGs may be NAD27 or NAD83. The Albers projection - NAD83 datum combination is recommended for Department of Fish and Game use. Further information about DRG products is provided below:

1:24,000-scale (24K) / 7.5-minute series DRG images

1:100,000-scale (100K) / 30 by 60-minute series DRG images

1:250,000-scale (250K) / 1 by 2-degree series DRG images

 

Option #1 - Download free individual DRG images on the Internet

DRG images for California are available for free download from the California Spatial Information Library (CaSIL) through the Cal-Atlas website:
http://www.atlas.ca.gov

Here are some tips on acquiring DRGs on the Internet:

  • Download the appropriate index shapefiles (above) and use them to determine file names for the individual images or mosaics you need. Acquire additional data as necessary from CaSIL or other sources to use as background reference information.
  • If you need to unzip the DRGs once downloaded, you can use software such as WinZip (which can be purchased or downloaded for evaluation from http://www.winzip.com).

DRGs are also available for free download from other sites, including:
http://www.gisdatadepot.com (GIS Data Depot / GeoCommunity)
http://datagateway.nrcs.usda.gov (USDA NRCS Geospatial Data Gateway)

 

Option #2 - Order DRG images on CDs or DVDs

CDs or DVDs of DRG images can be ordered and mailed to DFG employees at no cost. Here are the current DRG sets available:

  • Statewide 24K DRG Mosaics, Albers NAD83, MrSID format (click here for ordering information).
  • Statewide 24K DRG Mosaics, Albers NAD83, TIFF format (click here for ordering information).
  • Statewide 100K & 250K DRG Mosaics, Albers NAD83, MrSID and TIFF format available together on 1 DVD.
  • DRG Index Shapefiles, Albers NAD83, can be downloaded above or are available together on 1 DVD.
  • Custom sets can be written for those employees who cannot easily download the files from the Internet.
  • Email requests to the GIS Service Center (geodata@dfg.ca.gov).

 

Option #3 - Access DRG images through DFG Internet Map Services

DFG provides map services that stream DRG images directly into your GIS software or web browser from across the Internet. A high-speed Internet connection is recommended. This is an efficient way to access the imagery as-needed without having to store all the data locally.

Here are some options for DFG employees to access the map services:

  • If you just want to view topo maps in a web browser, most of the DFG Internet mapping applications include them as background layers. For example, pick one of the applications at http://imaps.dfg.ca.gov, zoom in, and the appropriate DRGs will draw based on your viewing scale and extent (keep zooming in to see more detail).
  • For GIS software users, DFG's Spatial Data Framework CD includes GIS projects with pre-loaded connections to the DRG map services. The GIS projects work with software such as ArcGIS ArcMap and ArcExplorer Java Edition. Details and ordering information are available here