1:24k Digital Raster Graphic - Collars Removed [Minnesota]
Minnesota Geospatial Commons
Full Details
- Title
- 1:24k Digital Raster Graphic - Collars Removed [Minnesota]
- Description
- A digital raster graphic (DRG) is a scanned image of an U.S. Geological Survey (USGS) standard series topographic map, including all map collar information. The image inside the map neatline is georeferenced to the surface of the earth and fit to the Universal Transverse Mercator projection. The horizontal positional accuracy and datum of the DRG matches the accuracy and datum of the source map. The map is scanned at a minimum resolution of 250 dots per inch. DRG's are created by scanning published paper maps on high-resolution scanners. The raster image is georeferenced and fit to the UTM projection. Colors are standardized to remove scanner limitations and artifacts. The average data set size is about 6 megabytes in Tagged Image File Format (TIFF) with PackBits compression. DRG's can be easily combined with other digital cartographic products such as digital elevation models (DEM) and digital orthophoto quadrangles (DOQ). DRG's are stored as rectified TIFF files in geoTIFF format. GeoTIFF is a relatively new TIFF image storage format that incorporates georeferencing information in the header. This allows software, such as ArcView, ARC/INFO, or EPPL7 to reference the image without an additional header or world file. Within the Minnesota Department of Natural Resources Core GIS data set the DRG's have been processed to be in compliance with departmental data standards (UTM Extended Zone 15, NAD83 datum) and the map collar information has been removed to facilitate the display of the DRG's in a seamless fashion. These DRG's were clipped and transformed to UTM Zone 15 using EPPL7 Raster GIS. DRGs are a useful backdrop for mapping a variety of features. Colors representing various items in the image (contours, urban areas, vegetation, etc.) can be turned off or highlighted depending on the mapping application. In ArcView this is done by choosing the "Colormap" option when editing the DRG theme's legend. A variety of other ArcView tools exist to make working with DRGs easier. Also included: Metadata for the scanned USGS 24k Topograpic Map Series (also known as 24k Digital Raster Graphic). Each scanned map is represented by a polygon in the layer and the map date, photo revision date, and photo interpretation date are found in the corresponding attribute record. This layer facilitates searching for DRGs which were created or revised on or between particular dates. Also useful for ascertaining when a particular map sheet was created., The DRG is used for validating digital line graphs (DLGs) and for DLG data collection and revision. The DRG can help assess the completeness of digital data from other mapping agencies. It can also be used to produce hybrid products. These include combined DRGs and DOQs for revising and collecting digital data, DRGs and DEMs for creating shaded-relief DRGs, and combinations of DRG, DOQ, and DLG data. Although a standard DRG is an effective mapping tool, its full potential for digital production is realized in combination with other digital data. Clipping the collar information allows seamless viewing of adjacent DRGs. Standardizing the UTM zone and the datum matches the data with many other statewide datasets available in Minnesota. , Current as of 2003
- Creator
- U.S. Geological Survey (USGS) and Minnesota Department of Natural Resources (DNR)
- Publisher
- Minnesota Geospatial Commons
- Rights
- None
- Access Rights
- Public
- Format
- Files
- Language
- English
- Date Added
- August 20, 2023
- Provenance Statement
- The metadata for this resource was last retrieved from the Minnesota Geospatial Commons on 2025-08-26.
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