Digital elevation model

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Draft

“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 15:56, 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 15:56, 12 May 2010 (UTC)).

File Formats

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 15:56, 12 May 2010 (UTC)).

Digital elevation models

“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 It has been superseded by the USGS's own SDTS format but the format remains popular due to large numbers of legacy files, self-containment, relatively simple field structure and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 15:56, 12 May 2010 (UTC))

“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 15:56, 12 May 2010 (UTC))

“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 15:56, 12 May 2010 (UTC))

General puporse 3D formats

Available terrain maps

GTOPS30

GTOPO30 is is a global digital elevation model (DEM) 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
Advanced Spaceborne Thermal Emission and Reflection Radiometer

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).

To sort out

Printing with a RepRap printer

(e.g. a RapMan)

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