Digital elevation model

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Draft

Introduction

“A digital elevation model (DEM) is a digital representation of ground surface topography or terrain. It is also widely known as a digital terrain model(DTM). A DEM can be represented as a raster (a grid of squares) or as a triangular irregular network.” (Wikipedia, retrieved 17:39, 12 May 2010 (UTC)).

A digital surface model (DSM) on the other hand includes buildings, vegetation, and roads, as well as natural terrain features. The DEM provides a so-called bare-earth model, devoid of landscape features. While a DSM may be useful for landscape modeling, city modeling and visualization applications, a DEM is often required for flood or drainage modeling, land-use studies, geological applications, and much more. (Wikipedia, retrieved 17:39, 12 May 2010 (UTC)).

See also:

Models and file Formats

-- This section badly needs revision and updating - Daniel K. Schneider (talk) 10:41, 21 March 2017 (CET)

Both digital elevation and surface models can either be represented as raster or vector graphics.

  • Raster data can present either just images (as in any image format like *.jpg*) or include specific data about a cell.
  • Vector data either can be points (locations), lines or polylines (e.g. for topographics lines or roads), or polygons.

“Additional non-spatial data can also be stored along with the spatial data represented by the coordinates of a vector geometry or the position of a raster cell. In vector data, the additional data contains attributes of the feature. For example, a forest inventory polygon may also have an identifier value and information about tree species. In raster data the cell value can store attribute information, but it can also be used as an identifier that can relate to records in another table.” (Wikipedia, retrieved 17:39, 12 May 2010 (UTC)).

Digital elevation models

USGS DEM
“The USGS DEM standard is a geospatial file format developed by the United States Geological Survey for storing a raster-based digital elevation model. It is an open standard, and is used throughout the world. It has been superseded by the USGS's own SDTS format but the format remains popular due to large numbers of legacy files, self-containment, relatively simple field structure and broad, mature software support.” (Wikipedia, retrieved 17:39, 12 May 2010 (UTC))
SDTS

“The The Spatial Data Transfer Standard (SDTS) is a robust way of transferring earth-referenced spatial data between dissimilar computer systems with the potential for no information loss. It is a transfer standard that embraces the philosophy of self-contained transfers, i.e. spatial data, attribute, georeferencing, data quality report, data dictionary, and other supporting metadata all included in the transfer.” (USGS, retrieved 17:39, 12 May 2010 (UTC))

DTED

“DTED (or Digital Terrain Elevation Data) is a standard of digital datasets which consists of a matrix of terrain elevation values. This standard was originally developed in the 1970s to support aircraft radar simulation and prediction.” (DTED (Wikipedia, retrieved 17:39, 12 May 2010 (UTC))

Other/combined models

SRTM
“The Shuttle Radar Topography Mission (SRTM) is a partnership between NASA and the National Geospatial-Intelligence Agency (NGA). Flown aboard the NASA Space Shuttle Endeavour (11-22 February 2000), SRTM fulfilled its mission to map the world in three dimensions.” (EORS.usgs.gov)
Advanced Spaceborne Thermal Emission and Reflection Radiometer

General pupose 3D formats

Available terrain maps

STRM

The Shuttle Radar Topography Mission (SRTM) Maps.

Download links:

GTOPO30

GTOPO30 is a global digital elevation model (DEM) of the whole world with a horizontal grid spacing of 30 arc seconds (approximately 1 kilometer). GTOPO30 was derived from several raster and vector sources of topographic information.

Download links:

Other

Links

Overviews

Visualization and GIS

(these are related subjects)

Overviews and indexes of File formats

Actors

Online maps to look at

(some can show relief).

  • Maps-For-Free.com. Allows to display various Layers on either satellite, terrain, relief or OSM view. Allows to take a picture (jpg).
  • GloVis (USGS Global Visualization) is an online search and order tool for selected satellite data. It includes
  • WIST (Warehouse Inventory Search Tool) is a web-based client to search and order earth science data from various NASA and affiliated centers, e.g. GloVis.
  • MRTWeb combines familiar capabilities of the USGS Global Visualization Viewer (GloVis) and the downloadable MODIS Reprojection Tool (MRT)

Software

Viewing
  • TerraLook (Wikipedia) a free satellite image viewing tool, developed by Sujoy Chaudhuri of Ecollage, India.
  • Google Earth (Wikipedia)
Multipurpose
  • ArcGIS (Wikipedia) Commercial group of geographic information system (GIS) software products produced by ESRI.

To sort out

Bibliography, links and footnotes

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