Digital raster graphics (DRGs) - also known as topographic maps
Digital Raster Graphics (DRGs) are optically scanned map images originally produced by the US Geological Survey (USGS). This page describes DRGs for the State of Wisconsin as acquired from USGS and used at the DNR.
As produced by the USGS, each DRG includes a "map collar" surrounding the map portion of each DRG and containing ancillary information about the printed map, such as scale bars, legend, and attribution. The "map collar" portion of the DRGs is reclassified to a distinct range of pixel values in the scanned image (values 20 through 32). This enables users of mapping software to optionally "turn off" the DRG map collar for display purposes.
DNR staff also converted the DRGs from the coordinate system in which they are produced by the USGS to the DNR's standard coordinate reference system, which is the Wisconsin Transverse Mercator coordinate system of 1983 based on the 1991 adjustment to the North American Datum of 1983. This coordinate system is known as WTM83, NAD83 (1991).
The DRGs available from the DNR are intended primarily for use with ArcGIS mapping software. DNR staff have received reports of problems in displaying these DRGs using other image viewing software, particularly AutoCAD. The main issue is that the DRGs appear "blurry" at scales which should normally result in adequate display quality. These problems are believed to be due to variations in the ability of different software to display all of the versions of compressed TIF formats currently in use. The users reporting viewing problems generally indicate that USGS-produced DRGs display correctly, so if you experience problems viewing the DNR-enhanced DRGs, we suggest you obtain the images directly from the USGS (refer to the link at the right-hand side of this page).
- Topo Maps Available on the DNR FTP Site
- All of the 1:24,000-scale digital topographic maps (digital raster graphics, or DRGs) for Wisconsin published by the US Geological Survey (USGS) will continue to be available for download from this location on the DNR Public GIS FTP site. The 24K DRGs are organized by folders corresponding to the 1-by-1-degree tiles used by the USGS for topographic mapping; an index graphic for those tiles is provided below .
- The statewide USGS 1:100,000-scale DRGs and tile index are available here .
- The statewide USGS 1:250,000-scale DRGs and tile index are available here .
- Linked from the Maps for America site, US Topo maps are available for free Web download through The USGS Store; please refer to the US Topo Quadrangles - Maps for America site for more information .
- This site provides both an interactive viewer for displaying topographic map information, and a free map download capability.