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 Alaska Geospatial Data Committee

US GeoData Product Descriptions and Fact Sheets

Digital Elevation Models (DEM)

  • DEM's are digital records of terrain elevations for ground positions at regularly spaced horizontal intervals (10-meter, 30-meter, and 2-arc second).

  • Level II DEM's are generated from digital contour line files derived from USGS topogrophic quadrangles and are available in 7.5-minute, 15-minute, and 1-degree units.

    DEM Fact Sheet

Digital Orthophoto Quadrangles (DOQ)

  • DOQ's are digital images of aerial photographs in which displacements caused by the camera and terrain have been removed. A DOQ combines the image characteristics of a photograph with the geometric qualities of a map.

  • The standard DOQ produced by the USGS is a black-and-white or color-infrared, 1-meter ground resolution, 3.75-minute image scanned from 1:40,000-scale quarter-quad centered photography produced under the National Aerial Photography Program.

    DOQ Fact Sheet

Digital Raster Graphics (DRG)

  • DRG's are scanned images of USGS topographic quadrangles including all map collar information. The image inside the map neatline is georeferenced to the Earth's surface. DRG's can be used in combination with DOQ's and elevation data to aid in the collection, review, and revision of other types of digital data, especially vector data.

    DRG Fact Sheet

Digital Line Graphs (DLG)

  • Vector representation in DLG-3 format of Public Land Survey System (PLSS), boundary, hydrography, hypsography, and transportation features as shown on USGS 7.5- and 15-minute topographic quadrangle maps. Please note that the PLSS catagory is portrayed only as reference system and does not contain information to the parcel level.

    DLG Fact Sheet

Digital Line Graphs (DLG) -- Core Content

  • Certain features, and some attribute information, found in full-content DLG-3 data are not collected (refer to DLG-3 Core fact sheet for comparison).

  • Due to the reduced feature content, less time is required to generate a core-content DLG, and collection costs are correspondingly reduced.

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Page Last Modified: Wednesday, 07-Dec-2016 11:56:30 AKST