RIO BLANCO
CHILE
Advantages of a Digital Elevation Model
Advantages of satellite imagery
Landuse
Erosion Risk
Geometrie Accuracy
Height Levels
Visualisation
Land Suitability
A DEM can be digitally derived from Stereo imagery (e.g.
aerial photography, dual SPOT images, SPOT LANDSAT)
or by digitizing existing contour maps. This ortho-image is
digitally generated on the basis of such a DEM. On the left
side of this ortho-image map some examples are shown
to demonstrate other applications of a DEM.
Various satellites (e.g. SPOT, LANDSAT, ERS) cover the
world in a continuous sequence creating images. Every
spot on earth is regularly monitored Within days after
collection the information is available on digital tapes. This
creates the opportunity for multitemporal analysis to control
processes which vary in time such as desertification.
A DEM can be an important tool to calculate
runoff which is highly influenced by the slope
percentage. The drainage pattern is derived
from the DEM to indicate areas where erosion
is most likely to occur.
Fields with known landuse lead the program to
classify all pixels with the same characteristics
to identical classes. In this example a landuse
map is made by means of Classification of a
SPOT multi spectral image.
In the spectral mode (XS) a SPOT image has
20 m spatial resolution while in the panchromatic
mode (P) the resolution comes down to10m.
This can be used to enhance the LANDSAT
images which have a better spectral resolution.
The DEM can be used to derive a thematic
elevation mapto improve topographic maps.
The contours on the ortho-image map are also
generated by the DEM. The elevation interval
can be adjusted for different use.
Using an ortho-image in combination with a DEM
an unique opportunity is found to visualise the
unknown or inaccessible areas. These can be
explored by 'flying' through the draped images.
The DEM supports a possible thematic map for
the solar aspect of the land. This can therefore,
in combination with other maps (e.g. soil maps)
be used to generate a land suitability map.
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Perspective view
Scale 1:250.000
SPOT multispectral image CNES
1 Scene KJ 673-416, June 12th 1990
[Digitally orthorectified, 20m resolution
i 1300 DEM 5600 above sealevel
Universal Transverse Mercator
Southern Hemisphere, Zone 19H
Ellipsoid: International 1924
Geodetic Datum: South American 1
Produced by:
For information
KLM AEROCARTO b.v Fruitweg9, 2525 KE The Plague The Netherlands
Telephone 31 70 3803311, Facsimile: 31 70 3897642, Telex 32456
