’ATIONS
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SCOP is a
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Output
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raster
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GIS-
Interfaces
numerical
output
other
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EM
tion model
terpolation
SCOP interpolates a highly densified grid model with variable
grid width (Kostli/Wild 1984) from irregularly distributed
points (mass points, spot heights) and lines (break lines, form
lines, border lines) of any origin. The measured lines are
rigorously stored in the DEM and are therefore available for all
DEM applications. A subdivision of the DEM area into small
rectangular computing units enables the processing of huge
DEM projects even on personal computers. The data structure
is shown in fig. 2.
The DEM is stored as an index-sequential file with direct
access to local parts (Kóstli/Sigle 1986). Thus a very efficient
processing of the DEM data is guaranteed, with access times of
less than 0.1 sec. even in an extremely large DEM.
The SCOP DEM data structure is not exclusively used for the
storage of terrain heights, but it is also the data basis for
derived data like digital slope models or height difference
models. Those digital surface descriptions are called "SCOP
models" in the following.
Fig.2: DEM data structure
4. VOLUME COMPUTATION - A FIRST EXAMPLE
FOR DEM COMBINATION AND INTERSECTION
A volume computation from digital elevation models may be
done in two steps:
1. derivation of a height difference model
2. volume computation from the difference model for
predefined areas of interest (e.g. earthwork areas).
4.1 Derivation of a Height Difference Model
Two DEMs for the same area have to be given in the SCOP
DEM data structure. They may describe a former or existing
terrain, but also projected terrain forms.
The two DEMs may have different grid intervals and different
line information (break lines etc.). From the two DEMs the
height differences are computed and stored in the difference
model as shown in fig. 3 for an open mining area.
The difference model inherits the grid structure from one of the
DEMs and the line information from both DEMs. Thanks to
this, embankments and other important terrain features are
fully represented in the difference model.
difference model difference isolines
area no. area volume
1 cutting: 25402.48 144809.41
1 filling : 921.57 204.08
2 cutting: 1357.36 15569.44
filling : 0.00 0.00
3 cutting: 2219.11 6358.70
filling : 189.90 107.49
areas of interest results of volume computation
Fig. 3: Example of a volume computation
4.2 Volume Computation
It is the aim of a volume computation to determine the earth
volumes separated into cutting and filling for some areas of
interest (e.g. earthwork areas).
Areas of interest may be any areas within the difference model
defined by closed polygons. Cutting and filling are separated
by the intersection line of the two DEMs, which is the isoline
of height difference zero.
"ew — grid of the difference model
4 border of the area of interest
,^|— intersection line
(height difference zero)
|
I
7
7A
cn T break lines
J 4
À Fig.4.1: Lines for volume
z^ computation
Fig.4.2: Triangular prisms
879
