Digital Raster Graphics (DRGs) a.k.a. 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 enhanced by DNR.

More information about DRGs is available from:

• USGS Digital Raster Graphics Web Site [exit DNR].
• Wisconsin Geological and Natural History Survey (WGNHS) - purchase printed topographic maps at their Madison Map Sales Office or call (608) 263-7389

• DNR-enhanced DRGs Overview
• Metadata for DRGs [PDF 0.3MB]
• TIF Format Compatibility Issues
• View or Download DRGs Data & Documentation
• Map of 1x1 Degree Cell Index for 7.5 Minute DRGs

DNR-enhanced DRGs Overview

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 DNR-enhanced DRGs is reclassified to a distinct range of pixel values in the scanned image (values 20 through 32). This enables ArcView users to optionally "turn off" the DRG map collar for display purposes.

We also converted the DRGs from the coordinate system in which they are produced by the USGS to the coordinate reference system in use at the DNR, 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).

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TIF Format Compatibility Issues

The DNR-enhanced DRGs available from the Enterprise Data Management Section are intended primarily for use with ArcView or ArcInfo. Our testing, and reports from various users of these DRGs , indicates that image display quality is satisfactory using ArcView or other ESRI-produced software. No warranty is made regarding the compatibility of DNR-enhanced DRGs with a particular type of image viewing software.

We have received reports of problems in displaying these DRGs using image viewing software other than ArcView or ArcInfo, and particularly AutoCAD. The main complaint 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 the 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 top of this page).

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View or Download DRGs Data & Documentation

Our application allows the user to identify, view, and download individual 7.5-minute (1:24,000-scale) Digital Raster Graphics (DRGs) for Wisconsin. The 1:24K DRGs accessible via this site are provided in Tagged Image File (TIF) format. These files are presented strictly "as is" and the DNR is not available to provide technical assistance and support for the use of DRGs.

NOTE: Due to the large number of people trying to download DRGs from this site during business hours, you may experience access problems. If so, you may have better results downloading DRGs outside of business hours. If you are trying to download large numbers of DRGs from the DNR site and encounter problems, send email to: the DNR Bureau of Technology Services.

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1x1 Degree Cell Index Graphic for 7.5 Minute DRGs