139
Figure 8: Comparison of hillshaded DEMs: On left side is
DEM, interpolated from contour lines only and on the right
DTM 25 for the Alpine test region (2).
7. FURTHER PLANS
Results of the case study with only few datasets -
basically contour lines and DEM 100, show possibility for
drastical improvement of old DEM 100 and also current
(not yet completely finished) DEM 25.
For the next stage special emphasis will be done to
improvement of interpolation parameters and
simultaneously add new available data with high
accuracy. There are many data available in digital
databases which haven’t been used, but they will be
sources for modeling in the future on test regions:
local DEMs available for Slovenia including DEM
produced with SAR interferometry,
register of the buildings,
other geodetic points (cadastre, polygon, etc.),
hydrology (streams and lakes) and more.
The next will be data for improving morphological details
and other possibly data for general condensing input data:
photogremmetrically or otherwise captured
characteristic data - points and lines for terrain
details,
densification (condensing) of the model with
scattered data as it is laser altimetry at urban
and other areas, interesting for potential users or
with DEM produced with SAR interferometry.
After testing the quality of output DTM 25, reference
geodetic points will be also included in the model.
Interpolation process will be improved by using different
interpolation techniques with regard to relief morphology.
For DTM surface generation it is necessary to produce a
“DTM database” that must have the ability to be updated
with every improved new data and enable to quickly
produce the desired DTM / DEM (Rihtarsic and Fras,
1991). Such organization of data will lead to “dynamic
DTM database” for DTM production and back to
multiscale, “elastic grid” DEM production, suitable for GIS
analyses.
8. CONCLUSION
First, preliminary results, using integrated data approach
in the case study are very promising. DTM /DEM with
25 m grid size was produced for selected regions in
Slovenia with height accuracy of approx. 1 m for
predominantly flat and urban areas, 4 m for the hilly areas
and 10 m for the alpine areas.
With condensing additional, different quality data, height
accuracy could be for about 1/4 - 1/3 better than from
case study and general grid of 20 m would be reasonable
to cover whole area of Slovenia for the first next stage.
With methods presented in the article we can relatively
easy, cheaply and in short time produce the requested
high quality DTM for all Slovenia.
Acknowledgment
Special thanks go to Prof. Dr. Karl Kraus and his team
from Institute for Photogrammetry and Remote Sensing at
Vienna University of Technology for advices and access
to SCOP program package. We are much obliged to
Surveying and Mapping Authority of the Republic of
Slovenia for realizing the project to produce DEM 25 with
SAR interferometry.
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