Talk:Digital elevation model
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From Liu & Mason 2010 <ref name=Liu10></ref> | From Liu & Mason 2010 <ref name=Liu10></ref> | ||
| − | + | DEM's are a subgroup of [[Surface models]] (should there be an own category?) | |
and can be obtained by | and can be obtained by | ||
# [[Photogrammetry]] | # [[Photogrammetry]] | ||
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above a certain level, i.e. a [[Geodetic datum]]. It may represent the [[Wikipedia:Elevation|elevation]] of the bare earth, | above a certain level, i.e. a [[Geodetic datum]]. It may represent the [[Wikipedia:Elevation|elevation]] of the bare earth, | ||
or include objects as buildings or tree canopies <ref name=Liu10> Liu, J. G. & Mason, P. Essential Image Processing and GIS for Remote Sensing. (John Wiley & Sons, 2010).</ref>. | or include objects as buildings or tree canopies <ref name=Liu10> Liu, J. G. & Mason, P. Essential Image Processing and GIS for Remote Sensing. (John Wiley & Sons, 2010).</ref>. | ||
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| + | [[Image:Dem_grey.jpg|A DEM of Göttingen and the surrounding area. High elevation is displayed in white, low elevation in black. |thumb|right|500px]] | ||
| + | |||
| + | == 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<ref name=Liu10></ref>. | ||
| + | |||
| + | More specific forms of DEMs sometimes appearing in forestry related publications | ||
| + | are '''Digital Vegetation-height Models (DVM)''' <ref name=Nuske04>Nuske, R. S. & Nieschulze, J. The vegetation height as a tool for stand height determination: An application of automated digital photogrammetry in forestry. Allg. Forst Jagdztg. 175, 13–21 (2004).</ref> or '''Digital Canopy Height Models (DCHM)'''<ref name=Patenaude04>Patenaude, G. et al. Quantifying forest above ground carbon content using LiDAR remote sensing. Remote Sensing of Environment 93, 368–380 (2004).</ref>. | ||
| + | |||
| + | == Creation of DEMs == | ||
| + | ===Sources=== | ||
| + | ====Photogrammetry==== | ||
| + | ::''Main article [[Photogrammetry]]'' | ||
| + | |||
| + | Digital elevation models may be obtained by [[Aerial photography|aerial photography]] | ||
| + | and spaceborne instruments such as [[:wikipedia:Advanced_Spaceborne_Thermal_Emission_and_Reflection_Radiometer|ASTER]], [[:wikipedia:IKONOS|IKONOS]] | ||
| + | or [[:wikipedia:SPOT_(satellite)|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]]'' | ||
| + | |||
| + | SAR, also referred to as InSAR (Interferometric Synthetic Aperture Radar), | ||
| + | provides an acoustic approach to acquire remote sensing data. | ||
| + | Acoustic signals are transmitted and the duration of the reflected signal | ||
| + | reaching the sensor is measured. An advantage | ||
| + | to the optical systems is it's weather independence, as acoustic noise | ||
| + | is able to penetrate clouds <ref name=Liu10></ref>. | ||
| + | |||
| + | ===GIS processing=== | ||
| + | In a [[:wikipedia:Geographic_information_system|GIS]], DEMs may be derived | ||
| + | from [[vector]] data, where each point contains an estimation of the local terrain | ||
| + | height. The DEM is then constructed by [[interpolation]] of these points. | ||
== DEMs in forestry == | == DEMs in forestry == | ||
| + | DEMs may be used in forestry for various research objectives, | ||
| + | such as: | ||
| + | * Measuring stand height<ref name=Nuske04></ref> | ||
| + | * Estimating the mass of above ground carbon <ref name=Patenaude04></ref> | ||
| + | * Hydrological objectives, such as assessing drainage<ref name=Zhao08>Zhao, Z. et al. Model prediction of soil drainage classes based on digital elevation model parameters and soil attributes from coarse resolution soil maps. Can. J. Soil Sci. 88, 787–799 (2008).</ref> or calculating water flow paths<ref name=Korkalainen08>Korkalainen, T., Laurén, A., Koivusalo, H. & Kokkonen, T. Impacts of peatland drainage on the properties of typical water flow paths determined from a digital elevation model. Hydrology Research 39, 359 (2008).</ref> | ||
| + | |||
| + | Digital elevation models are frequently used to estimate other terrain properties, such as [[Slope|slope]], | ||
| + | [[Aspect|aspect]] and [[Hillshade|hillshade]], | ||
| + | or to create [[Viewshed|viewsheds]]. | ||
| + | |||
| + | == Related articles == | ||
| + | * [[Creating a DEM from vector data]] | ||
== References == | == References == | ||
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== External links == | == External links == | ||
| − | [http://en.wikipedia.org/wiki/Digital_elevation_model Digital elevation model on Wikipedia] | + | * [http://en.wikipedia.org/wiki/Digital_elevation_model Digital elevation model on Wikipedia] |
| + | * [http://srtm.usgs.gov/index.php SRTM data from the U.S. Geological Survey] | ||
Latest revision as of 09:58, 28 June 2013
Contents |
[edit] Article discussion
- This section is meant solely for discussion purposes.
For a draft of the article, see #Article draft.
- This section is meant solely for discussion purposes.
[edit] Possible contents and links
From Liu & Mason 2010 [1] DEM's are a subgroup of Surface models (should there be an own category?) and can be obtained by
Related articles already existing in this wiki are:
[edit] 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].
[edit] 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].
More specific forms of DEMs sometimes appearing in forestry related publications are Digital Vegetation-height Models (DVM) [2] or Digital Canopy Height Models (DCHM)[3].
[edit] Creation of DEMs
[edit] Sources
[edit] 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.
[edit] 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.
[edit] SAR interferometry
- Main article SAR interferometry
SAR, also referred to as InSAR (Interferometric Synthetic Aperture Radar), provides an acoustic approach to acquire remote sensing data. Acoustic signals are transmitted and the duration of the reflected signal reaching the sensor is measured. An advantage to the optical systems is it's weather independence, as acoustic noise is able to penetrate clouds [1].
[edit] GIS processing
In a GIS, DEMs may be derived from vector data, where each point contains an estimation of the local terrain height. The DEM is then constructed by interpolation of these points.
[edit] DEMs in forestry
DEMs may be used in forestry for various research objectives, such as:
- Measuring stand height[2]
- Estimating the mass of above ground carbon [3]
- Hydrological objectives, such as assessing drainage[4] or calculating water flow paths[5]
Digital elevation models are frequently used to estimate other terrain properties, such as slope, aspect and hillshade, or to create viewsheds.
[edit] Related articles
[edit] References
- ↑ 1.0 1.1 1.2 1.3 Liu, J. G. & Mason, P. Essential Image Processing and GIS for Remote Sensing. (John Wiley & Sons, 2010).
- ↑ 2.0 2.1 Nuske, R. S. & Nieschulze, J. The vegetation height as a tool for stand height determination: An application of automated digital photogrammetry in forestry. Allg. Forst Jagdztg. 175, 13–21 (2004).
- ↑ 3.0 3.1 Patenaude, G. et al. Quantifying forest above ground carbon content using LiDAR remote sensing. Remote Sensing of Environment 93, 368–380 (2004).
- ↑ Zhao, Z. et al. Model prediction of soil drainage classes based on digital elevation model parameters and soil attributes from coarse resolution soil maps. Can. J. Soil Sci. 88, 787–799 (2008).
- ↑ Korkalainen, T., Laurén, A., Koivusalo, H. & Kokkonen, T. Impacts of peatland drainage on the properties of typical water flow paths determined from a digital elevation model. Hydrology Research 39, 359 (2008).
