Revision as of 13:34, 25 May 2013

Article discussion

This section is meant solely for discussion purposes.
For a draft of the article, see #Article draft.

Possible contents and links

From Liu & Mason 2010 ^[1] DGM's are a subgroup of Surface models (should there be an own category?) and can be obtained by

1. Photogrammetry
2. Laser altimetry
3. SAR inferometry

Related articles already existing in this wiki are:

• Creating a DEM from vector data
• Evaluation of digital elevation models

Article draft

DEM stands for Digital elevation model. It can be represented as a regular grid of points or as a Triangular irregular network of points. DEMs are the basis for digitally produced relief maps.

Digital elevation models are sets of data representing the estimated height of a surface above a certain level, i.e. a Geodetic datum. It may represent the elevation of the bare earth, or include objects as buildings or tree canopies ^[1].

Types of DEMs

There are no official Definitions of different subgroups of digital elevation models, but the probably most used terms are Digital surface model (DSM) and Digital terrain model (DTM); the first model may quantify the height of the earth including objects on it's surface, while the latter models the elevation of the mere ground. Still, sometimes both terms are used to describe bare-earth models, leaving the original Digital elevation model term for models including objects above ground level^[1].

Creation of DEMs

Photogrammetry

Main article Photogrammetry

Digital elevation models may be obtained by aerial photography and spaceborne instruments such as ASTER, IKONOS or SPOT. The basic principle of photogrammetry is the retrieval of photographs from at least two different positions, which makes the measurement of object heights possible.

Laser Altimetry

Main article Laser altimetry

Also known as LiDAR, laser altimetry has revolutionized the acquisition of DEM data.

LiDAR devices send light pulses to earth and measure the reflection of the ground or objects on it. Time differences between reflected light pulses can be measured, enabling the measurement of object hights.

SAR interferometry

Main article SAR interferometry

DEMs in forestry

Related articles

References

1. ↑ ^{1.0 1.1 1.2} Liu, J. G. & Mason, P. Essential Image Processing and GIS for Remote Sensing. (John Wiley & Sons, 2010).

External links

Digital elevation model on Wikipedia