2.2 Data capture for the digital terrain model
The national DTM with an average point density of
50 m has been continuously updated since 1988
and upgraded with structural information. Scale:
1:15,000. Sampling method: grid of 50 m and
supplementation of relief structures (break lines,
form lines, singular points).
For revision purposes and in support of the data
correction, the contour lines are calculated by
means of the SCOP program after compilation, and
the images are superimposed on the stereo model.
At present, the compilation status according to the
current method amounts to approx. 30 % of the
Austrian territory.
2.3 Data capture for the topographic model
The topographic model (TM) is a digital landscape
model. It represents the earth's surface according to
topographic aspects and consists of primary data in
vector form which have not been changed by carto-
graphic procedures such as generalization and sym-
bolic feature codes. The structure of the landscape
is defined in an object type catalogue according to
object ranges, object groups and object types. A
more detailed description of the objects is provided
by means of integration with attributes.
Apart from manual digitizing of 1:10,000 ortho-
photos, digital compilation of aerial images (approx.
1:15,000 or 1:30,000) is also used for continuous
updating and useroriented supplementation,
especially in the object range "traffic".
2.4 Maintenance and application of the digital
elevation model - data base (DEM-DB)
At present, a total of approx. 105 individual points
from photogrammetric compilation are maintained
in a data base together with structural information.
Besides the original data, fully interpolated grids (25
m) are also maintained and recalculated auto-
matically on every update of the original data. Thus,
grids with any randomly-selected grid size can be
derived at any time for the data output.
The most important application of the digital
elevation model is the production of orthophotos
which are primarily. used for the further updating of
the topographic map 1:50,000 and the continuous
updating of the topographic model. These ortho-
photos have been produced digitally since 1994. A
total of some 1,500 orthophotos are produced
annually with scales ranging from 1:5,000 to
1:25,000. Further applications of the DEM-DB
include the derivation and output of contour line
plans, perspective views and hill shading.
2.5 Technical hardware:
5 Wild PUGx point transfer devices; 1 Leica BC3
analytical workstation (aerotriangulation); 8 Leica
BC3 analytical workstations with RISIS image
superimposition systems (DEM sampling and topo-
graphic model); 1 HP 715/50 workstation (Digital
Elevation Model Data Base); 1 PS/1 photo scanner
(used jointly with University of Technology and
2
International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B6. Vienna 1996
University of Agriculture, Vienna); 1 Digital photo-
grammetric workstation (Image Station of Inter-
graph) for orthophoto production; 8 Graphic work-
stations (PC 486, PC Pentium)
3 Cadastral Photogrammetry (Com. IV)
The division of cadastral photogrammetry carries
out the applications for cadastral purposes on a
national level. Depending on the posed problem the
method of aerial photogrammetric compilation
supports the
— determination and demarcation of types of soil
exploitation
— determination of feature lines and feature points
— quality control and quality improvement of the
digital cadastral map.
Its tasks also include photogrammetric restitutions
from historical flight missions for the documentation
of historical topographic facts and photogrammetric
compilations of topographic cadastre feature lines
for administrative boundaries.
The following basic information is applied to per-
form these tasks:
— Scale 1:10,000 colour photographs for the photo-
grammetric compilation of buildings and feature
lines.
— Scale 1:15,000 colour infrared photographs for
the photogrammetric compilation of land-use
boundaries and feature lines. :
= Scale 1:30,000 B/W photographs for the photo-
grammetric compilation of those areas which are
not yet included in the project of the digital
cadastral map. In this case the cadastral map is
updated for the valuation of farm land: i.e. up-
dating of boundaries for the demarcation of agri-
culturally cultivated areas from uncultivated
areas.
For preparation of the photogrammetric compi-
lation, enlargements and transparencies are
delivered to the respective local surveying offices in
order to establish an interpretation key for the
various types of cultivation. The areas to be
updated are interpreted and depicted in the aerial
photograph enlargements. The aerial photographs
are classified in a stereo model according to given
object classes and digitally analyzed. The digital
results are transferred to the local surveying offices
after the appropriate processing and serve for the
evaluation of the digital cadastral map.
The technical equipment of the division is:
10 Leica BC3 analytical workstations with RISIS
image superimposition systems; 4 Graphic work
stations (PC 386, PC 486, PC Pentium); 1 PC 386
linked to the real estate data base
4 Remote sensing (Com. IV)
Combined with a geographic information system,
three remote sensing systems were put into
operation at the end of 1995. Fields of activities: use
of remote sensing data for topographic mapping as
well as the interpretation of land use and land cover
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