DIGITAL ELEVATION MODELS (DEM)

Source:   Nebraska Department of Natural Resources Processed by:   Data Bank      (KM) A Digital Elevation Model (DEM) is a sampled array of elevations for a number of ground positions referenced horizontally and are usually spaced at regular intervals. The DEMs are produced in 7.5 minute quadrangle units which correspond to USGS 7.5 topographic maps with contour lines spaced at 10 feet interval and drawn to 1:24,000 scale. The level-2, 30-meter interval, DEMs are elevation data generated from hypsography (contours) Digital line graphs (DLGs) that have been processed or smoothed for consistency and edited to remove identifiable systematic errors. The DEMs are referenced horizontally to the NAD 27 and UTM projections (Zone 13, 14 & 15), and have a root mean square error (RMSE) of one half of the contour interval. The elevation units are in feet relative to the National Geodetic Vertical Datum of 1929 (NGVD29). The following Information Resources are available: DEM-30m metadata DEM-10m metadata Sample of DEM coverages. DEM National standards Quadrangle Indentification Map (28" X 45") Availability of DEMs (10-meter) The Nebraska Department of Natural Resources, in cooperation with the U. S. Geological Survey, developed 10-meter interval, Level 2, DEMs for the State of Nebraska. These DEMs are produced in 7.5 minute quadrangle units drawn to 1:24,000 scale, and are referenced to NAD 27 and UTM projections. The elevation units are in feet relative to NGVD 1929. Following options are available to retrieve 10-meter DEMs: DNR Map Interface Identify and download DEMs click on both active and visible layers of the Quad (DEM) dataset and click the "refresh map" button on the interactive map. Zoom in using the magnifing glass tool with the plus sign, then click hyperlink(lightning bolt) from the tool box and click the proper quadrangle to download the DEM. Provides access to both 10 and 30 meter DEMs. 10-meter DEM Text Interface. DNR FTP Site - (10-meter) The DEMs may require 1MB to 2MB of storage space per 7.5 minute quadrangle. The transmission of data over high-speed Internet lind could take 15-minutes or more per DEM coverage. The transfer of data at communication speeds less that 56KB/sec is generally not recommended. Retrieval of DEMs (30-meter) The Nebraska Department of Natural Resources (DNR) in cooperation with the U.S. Geological Survey, developed Level-2, 7.5 minute, 30-meter interval DEMs for the entire state of Nebraska. These DEMs are available through the Department of Natural Resources website and are also available upon request from the agency. Following Options are available to retrieve 30-meter DEMs: DNR Map Interface To identify and download DEMs click on both active and visible layers of the Quad (DEM) dataset and click the "refresh map" button on the interactive map. Zoom in using the magnifing glass tool with the plus sign, and click hyperlink(lightning bolt) from the tool box and click the proper quadrangle to download the DEM. Provides access to both 10 and 30 meter DEMs. 30-meter DEM Text Interface. DNR FTP Site - (30-meter) Display of DEMs A GIS (Geographic Information System) software is required to display DEM coverages. A copy of a freeware software called "DEM3d" is available from the Mid Continent Mapping Center (MCMC), U.S. Geological Surveuy. It can be downloaded from the MCMC Web site. User Request Comments and Suggestions   [ DNR Home ] [ Administration/Legal ] [ Surface Water ] [ Ground Water ] [ Data Bank ] [ Field Offices ] [ Planning & Assistance ] [ Floodplain & Dam Safety ] [ Resource Mgt Funds ] [ Site Index/Table of Contents ] [ Contact Us ] [ Need Help! ] [ Newsletter ] [ Staff Directory ] [ DNR Frequently Used Forms ] [ Work For Us ] [ Links ] [ Search This Site! ] [ Frequently Used Sites ] [ Security, Privacy & Accessibility Policy ] [ State of Nebraska ]