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	US GeoData Digital Elevation Models, Fact Sheet 040-00 (April 2000)
		DEM data for 1-degree units are collected from topographic map sources, ranging from the 7.5-minute map series to the 1- by 2-degree map series, or from photographic sources by using image correlation systems.
		DEM data are produced by the National Imagery and Mapping Agency (NIMA) in l- by 1-degree units that correspond to the east or west half of the USGS 1- by 2-degree topographic quadrangle map series (1:250,000-scale) for all of the United States and its territories.
		DEM data accuracy is derived by comparing linear interpolation elevations in the DEM with corresponding map location elevations and computing the statistical standard deviation or root-mean-square error (RMSE).
	mac.usgs.gov /isb/pubs/factsheets/fs04000.html (1287 words)

	USGS 300 Meter Resolution, 1-Degree Digital Elevation Models (DEM) for CONUS, Alaska, Hawaii, Puerto Rico, and the U.S. ...
		The accuracy of a DEM is dependent upon the level of detail of the source and the grid spacing used to sample that source.
		DEMs are edited to correctly depict elevation surfaces that correspond to water bodies of specified size.
		Level 2 DEM: A vertical RMSE of one-half of the contour interval (of 100,000-scale source), determined by the source map, is the maximum permitted.
	www.epa.gov /ost/basins/metadata/dem.htm (1725 words)

	GTOPO30 Documentation (Site not responding. Last check: 2007-10-21)
		USGS 1-degree DEM's with a horizontal grid spacing of 3-arc seconds (approximately 90 meters) were used as the source data for the continental United States, Alaska, and Hawaii.
		For instance, when viewing the DEM data as an image either in shades of gray or color, the artifacts may be hidden, depending on the number of shades or colors used.
		This effect is common in DEM's produced by gridding of contour data in which the interpolation process favors elevations at or near the contour values, thus leading to a greater frequency of those elevations.
	edcdaac.usgs.gov /gtopo30/README.html (6196 words)

	USGS & GTOPO30 DEM Geometry Import Converter
		DEM datasets typically contain 60000 or more quadrilateral polygons, or 1200000 triangles (for a 258x258 resolution sample; the maximum DEM dataset size if 2050x2050 which would result in 4.2 million quadrilaterals or 8.4 million triangles).
		This texture varies the color of the DEM data according to the elevation and slope of a polygon (the color varies from greens, to browns to whites at the highest altitudes).
		All DEM data are similar in logical data structure and are ordered from south to north in profiles that are ordered from west to east.
	www.okino.com /conv/imp_dem.htm (2548 words)

	DEM Tools (Site not responding. Last check: 2007-10-21)
		This package is useful for previewing DEM data sets and wandering around in virtual representations of various places on the planet.
		DEM tools were designed and compiled on a Linux system using the OpenGL Mesa, GLUT, and GTK libraries.
		DEM Tools is Copywrite © 1998 by Eric Kasten (and possibly others who may later contribute code), but is distributable under the GNU Public License (see the file COPYING that comes with the package).
	www.arq.net /~kasten/demtools (452 words)

	[No title] (Site not responding. Last check: 2007-10-21)
		The 1 Degree DEM provides coverage in one by one degree blocks and is available for all of the contiguous United States, Hawaii and Alaska.
		This original DEM of Australia was calculated by Moore and Simpson (1982) using the minimum curvature interpolation procedure of Briggs (1974) applied to approximately 320,000 point elevations.
		Since this in many cases this DEM is generated from the contours taken from a paper map (by one of three different procedures), the new contours are really second order.
	www.geo.ed.ac.uk /geoinfo/dem.send (12599 words)

	- DMTI Spatial - {Digital Elevation Model} (Site not responding. Last check: 2007-10-21)
		DEM data plays the same role as that of conventional paper contours and relief shading but with one key additional benefit: it provides a powerful analytical perspective.
		DEM data combined with DMTI Spatial's Clutter data is ideal for certain RF propagation applications such as wireless pager, microwave, PCS and other wireless network planning.
		DEM coverage is available by sheet (1:50,000 or 1:250,000) and custom defined areas such as along the Canadian/US Border or by Province.
	www.dmtispatial.com /digi_elev_model.htm (392 words)

	The GIS Weasel: Acquisition of Elevation Data in USGS DEM Format, East River, Gunnison River Basin, Colorado, USA (Site not responding. Last check: 2007-10-21)
		DEM will be used in these Problem Sets to refer to an ArcInfo GRID of elevation.
		The smallest DEM cell size is not always the best for modeling a watershed due to exponential increases in processing and disk space costs associated with decreased cell sizes.
		If you are working with elevation data from another part of the country and your newly created DEM shows a sliver of fl along the boundaries of pieces that were merged, then you need to do some additional processing to eliminate these cells.
	wwwbrr.cr.usgs.gov /weasel/manual/tutorial/class-set1.html (1619 words)

	Dukhtaran-e-Millat
		The DeM primarily operates in the Kashmir valley and its present strength is reported to be approximately 350.
		Later, in an interview published on September 9, she said that the current campaign was the "beginning of a comprehensive social reform movement based on true Islamic thought" and also asked women in Kashmir to stay away from government jobs.
		Security forces are yet to report any instances of terrorist strikes conducted by the DeM though they suspect that activists of the outfit act as couriers of arms and funds for various terrorist outfits operating in the State.
	www.satp.org /satporgtp/countries/india/states/jandk/terrorist_outfits/dukhtaran.htm (716 words)

	USGS Digital Elevation Models
		Although all are identical in the manner the data are structured, each varies in sampling interval, geographic reference system, areas of coverage, and accuracy; with the primary differing characteristic being the spacing, or sampling interval, of the data.
		DEM's may be used in the generation of three-dimensional graphics displaying terrain slope, apsect (direction of slope), and terrain profiles between selected points.
		A DEM file is organized into a series of three records, A, B, and C. The A record contains information defining the general characteristics of the DEM, including its name, boundaries, units of measurement, minimum and maximum elevations, number of B records, and projection parameters.
	rockyweb.cr.usgs.gov /elevation/dpi_dem.html (600 words)

	GIS - U.S. Fish and Wildlife Service
		The 1-degree DEM's (1:250,000 scale) are available for all of the contiguous United States, Hawaii, and portions of Alaska, Puerto Rico, and the Virgin Islands.
		DEM data by itself, unmanipulated, is not extremely useful.
		DEM data is raster in format, unlike the USGS DLG data which is vector.
	www.fws.gov /data/gisconv/demtools.html (827 words)

	DEM, Digital Elevation Model. (Site not responding. Last check: 2007-10-21)
		A Digital Elevation Model (DEM) is digital cartographic/geographic data in raster form.
		DEMs are derived from hypsographic data (contour lines) and/or photogrammetric methods using USGS 7.5-minute, 15-minute, 2-arc-second (30- by 60-minute), and 1-degree (1:250,000-scale) topographic quadrangle maps.
		DEMs are in UTM NAD27 zone 10 projection.
	craterlake.wr.usgs.gov /dem.html (96 words)

	Digital Elevation Model (DEM) Uncertainty: Evaluation and Effect on Topographic Parameters (Site not responding. Last check: 2007-10-21)
		The RMSE for USGS DEMs is calculated by comparing the DEM with 28 elevation points that reflect the "most probable" elevations at those locations (obtained from field control, aerotriangulated test points, spot elevations, or points on contours from existing source maps), not necessarily actual elevations (USGS, 1997).
		DEM errors exist and constitute uncertainty that is propagated with manipulation of the elevation data.
		DEM uncertainty may not matter, but it is not safe to make this judgement without a thorough evaluation.
	www.csulb.edu /~wechsler/Dissertation/P262/P262.html (7431 words)

	USGS TerraWeb: Antarctica DEM and AVHRR Stereo Images
		A Digital Elevation Model (DEM) is a representation of the topography/ elevation of an area on a pixel-by-pixel basis in a raster-image format.
		The digital number at a given DEM pixel is equal to the elevation at that location, usually in feet or meters (Antarctica DEMs are in meters).
		The Antarctica DEM data used in this project have a one kilometer spatial resolution, which is equal to the spatial resolution of the AVHRR mosaic.
	terraweb.wr.usgs.gov /TRS/projects/Antarctica/antdemsr.html (1003 words)

	TopoWeb -- Landscape Visualization (Site not responding. Last check: 2007-10-21)
		DEM files are height fields that represent the terrain.
		There should be one DEM file for the GTOPO and 1:250k data sets, and about 18 files for the 7.5 minute DEMs.
		For 7.5 minute DEMs only: These files are in the SDTS format and need to be converted to regular DEM format before they can be used in most programs.
	www.cis.ksu.edu /~dha5446/topoweb/demtutorial.html (599 words)

	USGS (U.S. Geological Survey) EROS, Sioux Falls, SD (Site not responding. Last check: 2007-10-21)
		Digital Elevation Models (DEMs) consist of a raster grid of regularly spaced elevation values that have been primarily derived from the USGS topographic map series.
		DEMs are available in Native format, written as ANSI-standard ASCII characters in fixed-block format.
		The average file size of a 30-meter DEM is 1.1 megabytes and 9.9 megabytes for a 10-meter DEM.
	edc.usgs.gov /products/elevation/dem.html (503 words)

	USGS SDTS format Digital Elevation Model data (DEM)
		DEMs consist of a sampled array of elevations for a number of ground positions at regularly spaced intervals.
		Using USGS DEMs in ArcView GIS - As GIS technology goes mainstream, we at the GeoCommunity have found a dramatic increase in the number of people downloading freely available data only to then be stumped when it comes to actually viewing or using the data.
		The new STDS DEM data can be used by ArcView3.2 but requires editing of the xxxxIDEN.DDF file - this posting to the discussion board provides details.
	data.geocomm.com /dem (1185 words)

	Presentation 1: DEM Uncertainty
		In a DEM, error is the difference between the true elevation at a point and the elevation shown in the DEM and can either be random (e.g.
		RMSE is essentially a standard deviation that assumes that the DEM errors are random and normally distributed, and is usually expressed in metres (for a DEM).
		They used calculated semivariograms and fractal dimensions to identify anisotropy in the DEM surfaces, which is (for the purposes of their paper) where the general pattern of variation is different in one direction than another over short distances.
	www.geog.ubc.ca /courses/geog516/talks_2000/dem_uncertainty.html (1339 words)

	DEM Tutorial - A basic guide for using Digital Elevation Models with Terragen
		A Digital Elevation Model (DEM) is a digital representation of a portion of the Earth's surface, or any planet's surface, derived from elevation measurements at regularly spaced horizontal intervals (sampling intervals).
		Simply stated, a DEM is a way of digitally recording the contours of the terrain.
		It is recommended you create a folder with a descriptive name to store each DEM, but leave the DEM file in its compressed state.
	www.cs.uh.edu /~somalley/DemTutorial (1398 words)

	Importing a DEM into ArcGIS (Site not responding. Last check: 2007-10-21)
		DEMs at TNRIS are identified by their USGS Quad Map name - see the USGS Quad and Quarterquad Locator Map to know which DEM you will need.
		The TNRIS DEMs are usually in the UTM coordinate system, NAD 27, Zone 14 for most of central Texas, and map units (x,y horizontal units) are meters.
		DEM data is available from the Federal government in SDTS format, and from many state agencies.
	www.ar.utexas.edu /Courses/parmenter/gis/arcgis_tips/DEM-import.html (783 words)

	DEM o'Graphics
		DEMs come in different flavors and a DEM may not be a.dem, but a.dt0.
		To determine the proportions, load into MD the DEM from which the grayscale was made and go to Modify/Map area/Full DEM to ensure you have a full DEM on screen, then to Info to find the Pixels on screen.
		The accompanying image illustrates a LightWave use of this variation: Four NIMA DTED tiles of areas of Kosovo and its environs were opened, merged and converted to grayscale in MD, with the same grayscale being used to create each of the objects in the image.
	www.3dartist.com /3dao/r/thomsnor/tndems.htm (1289 words)

	RI DEM/OTCA- Pollution Prevention Fact Sheet
		The Rhode Island Department of Environmental Management (DEM) Office of Technical and Customer Assistance's Pollution Prevention Section was created in 1987 to assist business and industry in their efforts to eliminate or reduce their use of toxic and hazardous materials.
		URI's Center for Pollution Prevention was created by the DEM in 1988 and continues to serve in a technical support capacity to DEM program staff throughout all phases of research, process design, and project implementation.
		DEM's Pollution Prevention Program is a non-regulatory business assistance program that offers free technical assistance to Rhode Island companies interested in incorporating pollution prevention into their processes.
	www.dem.ri.gov /programs/benviron/assist/pollut.htm (783 words)

	[No title]
		A DEM is normally generated by sampling a regular array of elevation values derived from topographic maps, aerial photographs etc., The basic data for a DEM is based on terrain elevation observations that are derived generally from one of three sources: digitized contours, photogrammetric data capture (including aerial photography and digital satellite imagery), and surveying.
		A DEM consists of a sampled array of elevations for a number of ground positions that are normally at regularly spaced intervals ¡(z§ ªÿó ¨DTM-1/1¨åDigital Terrain Model always means a land surface A DTM is the sum of all terrain specific information you have about an area including the elevation data (a DEM) itself.
		A DEM simply is a set of points defined in a three-dimensional cartesian space (X,Y,Z) that approximates a real surface - like a digital counterpart to nature.
	simon.cs.vt.edu /~mprg/DEM.ppt (435 words)

	Converting SDTS Dem Data from ArcUser magazine
		The model for using the SDTS DEM described here primarily uses data found the 7.5' Moab, Utah, quadrangle that was downloaded from the EROS site.
		Once the Moab DEM is located at the EROS site using either FTP by State or FTP by Graphics, take a careful look at its file name.
		This DEM requires a number of files that are all compressed inside a Tape Archive (TAR) file named 30.2.1.1006298.TAR.GZ.
	www.esri.com /news/arcuser/0799/webdata6.html (1666 words)

	Digital Terrain Modeling and Mapping
		An SDTS DEM is comprised of 18 separate files, arranged in a most unfriendly structure from a processing standpoint.
		DEM data for Canada is available in CDED format, which although it has its own specification is mostly identical to USGS ASCII format.
		DEM data for Australia is available in ER-Mapper format, which BLACKART v3.92 and higher can read.
	www.terrainmap.com /rm39.html (2208 words)

	2.5-minute Digital Elevation Model (DEM) for the Conterminous U.S. (Site not responding. Last check: 2007-10-21)
		The DEM originated with the EROS Data Center's 3-arc-second DEM's for the U.S. The DEM's were then mosaiced and resampled to 15-arc-second, and finally a modified Barnes filter (Barnes, 1964) was applied to the 15-arc-second coverage to smooth the DEM to 2.5-arc-minute resolution.
		This DEM provides a useful reference point from which to interpret the precipitation and temperature patterns, and is a clean coverage that can be used for other purposes.
		If you already have a DEM in your working projection/resolution, differences between the two DEMs (once the PRISM DEM is reprojected) may give you a feel for uncertainties introduced through (1) reprojection; (2) changes in resolution; and (3) basic differences in origins of the two DEMs.
	www.ocs.orst.edu /prism/docs/meta/dem_25m.htm (446 words)

	DEM (digital elevation model)
		the DEM standard is described in the USGS DEM Standards documents
		DEM data which has been converted to the SDTS format is referred to as "SDTS DEMs"
		RMSE of one-third of the contour interval is the maximum permitted.
	www.vterrain.org /Elevation/dem.html (502 words)

	National Mapping - Products, Digital Elevation Data
		A gridded DEM is one in the which the elevation points are spaced at a regular interval so as to create a grid or lattice.
		These grids can be directly observed or, more generally, they are computed from other elevation information such as contours or irregularly spaced spot heights.
		Please Note: Should you require gridded DEM data at a different grid spacing please contact the GA Sales Centre.
	www.ga.gov.au /nmd/products/digidat/dem.htm (93 words)

	Support Forums - USGS DEM Data
		There are numerous methods of handling DEM data, depending on what you want to do with it.
		There is a very simple utility program called DEMVERT that will process a DEM file into a grayscale bitmap image, in which the shades of grey depict the different elevations.
		A DEM should almost never be used in place of channel cross-sections or site-specific data, and of course, the DEM has little, if anything, to contribute to the knowledge of roadways and other structures that may affect stream channel and flood plain hydraulics.
	www.bossintl.com /forums/printthread/threadid/5285.html (1189 words)

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