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The Federal Office of Metrology and Surveying 
(Bundesamt für Eich- und Vermessungswesen) in Austria 
is doing data compilation by means of photogrammetry. 
They started in 1976 on analog stereo plotters by 
measuring profiles in aerial images with scale 1:30000. 
About ten years later the method changed to compiling 
profiles, breaklines, formlines and spot heights on 
analytical instruments from image material with scale 
1:15000. The complete data set consists of about 80 
millions of points. 
  
Figure 1: DTM from Austria (250 m x 250 m grid) 
(Data: Institute for Photogrammetry and Remote Sensing, TU Vienna) 
In Switzerland the Federal Office for Topography 
(Bundesamt für Landestopographie) uses a completely 
different approach. Topographic maps with scale 
1:25000 are scanned and contourlines, lakes and spot 
height points are extracted semi-automatically. 
  
Figure 2: DTM of Switzerland (250 m x 250 m grid) 
(Data: RIMINI Model, Federal Office for Topography) 
The situation at the Bavarian Office for Surveying 
(Bayerisches Landesvermessungsamt) is very similar to 
Austria. An essential difference is, that they are involving 
private companies for data compilation. 
Practically any method (manual digitizing of contour 
maps, tacheometric surveys, ...) can be used, which can 
deliver data economically, as long as the results are 3- 
dimensional and accuracy demands are fulfilled. 
3. CODING AND STRUCTURING OF TOPOGRAPHIC 
DATA 
Topographic data are organized either as line objects 
(ridge, dam, river, ...) single objects (spot heights, ...) or 
groups of point objects (photogrammetrically compiled 
grid data, ...). The meaning of an object is described by 
assigning feature code information to it. 
In practice two different approaches can be selected. One 
way is to code the data depending on geomorphological 
criteria (breakline, spot height, ...) or on how to influence 
different interpolation methods when calculating DTMs, 
while the other method is to assign really the actual 
meaning of the object (brook, dam, slope, ...). In 
consideration of long-term administration and usage of 
161 
the data, it is most desirable to keep as much coding 
information as possible. 
4. APPLICATION OF TOPOGRAPHIC DATA 
Of course topographic data are used to manage internal 
projects of surveying authorities or to work on behalf of 
other institutions. But an increasing demand emerges 
from private customers too. As long as the data are used 
only for internal purposes, it is rather easy to adapt data 
organization to a few typical production processes. Much 
more requirements have to be satisfied when executing 
requests from customers because of the variety of DTM 
products, data exchange formats and also because of 
strict deadlines. To enable efficient project management, 
all the necessary technical resources must be applicable 
in a highly flexible manner. 
5. SOFTWARE SOLUTION 
Based on these previously sketched general remarks and 
topics a concept for a software package (SCOP.TDM) 
has been designed and finally implemented at the 
Institute for Photogrammetry and Remote Sensing at the 
Vienna University of Technology. Although this paper 
deals mainly with managing country-wide topographic 
data, most parts of it are applicable for private surveying 
companies too. In this case more the inhomogeneity of 
the data is of importance than the huge amount data. 
5.1 Strategy 
The concept follows two main goals. Naturally most 
important is an efficient long-term storage and archiving 
of topographic data. This not only concerns geometry 
(coordinates) and coding, but also information about 
other data characteristics (accuracy, compilation method, 
authorized data users, ...), because these additional 
properties allow for good individual data selection. On the 
other hand it is necessary to provide a qualified basis for 
DTM application programs. Frequency of data access 
during operating on an actual project is much higher than 
access to an archive. This in any case enforces to store 
the topographic data permanently on the computers hard 
disk during work on a DTM project. But for archiving 
purposes also removable external direct access media 
should be considered as an acceptable alternative. In 
some situations there may be no clear distinction 
between project and archive phase when most parts of 
the data are used nearly all the time. So it should be the 
users decision to choose proper data organization. 
Finally another important topic is compatibility with other 
DTM packages by flexibly supporting different data 
formats for data import and export. 
5.2 Data Base Manipulation System 
A data base manipulation system (TOPDB) has been 
completely developed at the Institute for Photogrammetry 
and Remote Sensing at the Vienna University of 
Technology to store, manage and archive topographic 
data (Loitsch, Molnar, 1991). It is a relational data base 
system, that has been extended by geometric/topological 
elements and appropriate — geometric/topological 
operators to handle these elements. 
International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B2. Vienna 1996