Topography

Digital Elevation Models (DEMs)
A U.S. Geological Survey (USGS) Digital Elevation Model (DEM) is a regular array or grid of surface elevation sample points.  Sample points for DEMs at the 1:250,000-scale are separated by 3 seconds of latitude and longitude.  Sample points at the 1:24,000-scale are separated by 30 meters along the Universal Transverse Mercator (UTM) grid.  DEMs contain only elevation values associated with a series of x and y coordinates and header information.  The data user will need additional software to create viewable products such as contour maps, triangulated irregular networks (TIN), or shaded relief views.  For the portion of Minnesota which has been completed, DEMs can be ordered by contacting either the Minnesota Land Management Information Center (LMIC), 651-296-1211, or Rolla-Earth Science Information Center (ESIC), 573-308-3500 or 1-888-ASK-USGS.  For more information about DEMs, refer to the following: Base Maps for the 1990s - DEMs.

Digital Line Graphs (DLGs)
U.S. Geological Survey (USGS) Digital Line Graph (DLG) data are digital representations of cartographic information.  DLGs of map features are converted to digital form from maps and related sources. Intermediate-scale DLG data are derived from USGS 1:100,000-scale 30- by 60-minute quadrangle maps.  Intermediate-scale DLGs are sold in five categories: (1) Public Land Survey System, (2) boundaries, (3) transportation, (4) hydrography, and (5) hypsography.  Large-scale DLG data are derived from USGS 1:20,000-, 1:24,000-, and 1:25,000-scale topographic quadrangle maps.  Large-scale DLGs are sold in nine categories: (1) hypsography, (2) hydrography, (3) vegetative surface cover, (4) non-vegetative features, (5) boundaries, (6) survey control and markers, (7) transportation; (8) manmade features, and (9) Public Land Survey System.  All DLG data distributed by the USGS are DLG-Level 3 (DLG-3), which means the data contain a full range of attribute codes, have full topological structuring, and have passed certain quality-control checks.  DLG data can be ordered by contacting the Rolla-Earth Science Information Center (ESIC), 573-308-3500 or 1-888-ASK-USGS. 

Digital Raster Graphics (DRGs)
Digital Raster Graphics (DRGs) are scanned images of published U.S. Geological Survey (USGS) 1:24,000-, 1:100,000-, and 1:250,000-scale maps.  Each file consists of a full color 250 dpi raster file in GeoTIFF format and includes all legend information printed along the margins of the map.  The USGS distributes DRGs on CD-R and can be ordered by contacting the Rolla-Earth Science Information Center (ESIC), 573-308-3500 or 1-888-ASK-USGS. 

You may also order DRG's online from the USGS at: http://edcsns17.cr.usgs.gov/NewEarthExplorer/

A number of the DRGs along the Mississippi River, including areas within Minnesota as well as Wisconsin, Iowa, Illinois and Missouri, are available on-line at no charge from the Environmental Management Technical Center website: http://www.umesc.usgs.gov/data_library/available_data.html

Metadata:
Statewide 100 Meter EPPL7/EPIC2000 Data Set - a statewide data set that consists of approximately 400 raster-formatted data layers.  It is available on a single CD-ROM in either EPPL7 or ERDAS format.  The data themes cover a wide range of physical and biological variables along with administrative, political, sociodemographic, and transportation data.  The data collection unit for most of the variables is the 40-acre parcel.  Files have been subdivided into 100-meter by 100-meter grid cells and spatially corrected to provide improved geographic reference.  However, this processing step does not improve the original 40-acre resolution accuracy.  The data set is designed for use in regional and statewide planning, not for site-specific decision making.  This dataset is effectively the MLMIS100 county data set appended into a statewide coverage.  There is also a Twin Cities Metropolitan Area 30-meter EPPL&/EPIC2000 Data Set.

The statewide data set contains elevation, aspect, and slope layers for the State of Minnesota.  All three layers were derived from 1:250,000-scale U.S. Geological Survey (USGS) Digital Elevation Models (DEMs)

Digital Raster Graphics (DRG), 1:24,000 for Minnesota - A digital raster graphic (DRG) is a scanned image of a U.S. Geological Survey (USGS) topographic map. The scanned image includes all map collar information. The image inside the map neatline is georeferenced to the surface of the Earth using the UTM Zone and datum of the original map (most Minnesota DRGs are NAD27). 

Digital Raster Graphics (DRG), clipped 1:24,000 for Minnesota - The original USGS scanned image includes all map collar information and is georeferenced to the UTM zone and datum of the printed quad map. The Minnesota Department of Natural Resources has removed the collar information to allow seamless viewing of adjacent DRGs. Where needed, DNR has also projected the files to UTM Zone 15 (extended across Minnesota), NAD83.