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accuracy for DTM mapping exist. Here is one
from Hannover, where a 1 m DTM at 12.5 m
spacing exists.
The generated DTM over flat and hilly
territory showed that DTM’s to ± 5 m are
possible in flat areas, but that huge
discrepancies occur in wooded and hilly areas
where radar shadows and foreshortening
occur.
4. The scenario for the future
The future of mapping lies without doubt in
the capability to provide up-to-date base data
for a Geographic Information System.
Satellite images provide an economical input
of georeferenced image data which should be
merged with existing, old map data, which
can eventually be geometrically corrected by
the satellite data.
If reliable base data are available the can be
merged with thematic data obtained from
satellites and from ground surveys to be of
use to the planning authorities.
A survey of existing GIS efforts at various
scales based on a project orientation shows
that survey costs alone are tremendously
expensive per km 2 if not integrated. Cost
benefit ratios of 1:4 can be achieved through
data integration.
In Germany base data are already being sold
by the administrations instead of maps.
Digital orthophotos compare favourable in
price with vector data obtained by digitization
of maps. New map compilation would be
considerably more costly than the digital
orthophotos. Thus map updating via on
screen orthophoto digitization is an
economical necessity.
If satellite orthophotos at high resolution can
be provided cheaper than those of aerial
photos, then their market is clearly
established.
We have the new technology under control:
■ GPS
■ digital photogrammetry
■ remote sensing
■ GIS
We must find organizational structures which
permit integration of data.
The mapping process with isolated specialists
has to be transformed into a geoinformatics
process meeting the demands of society in an
efficient and economic manner.
In this task WG VI/3- Technology Transfer can
play a very important role.
The problems faced by our new generation of
mapping experts are less technical, but more
organizational.