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Both the topographic data market and the archive consist 
of two groups of tables. Some organizational and 
summary tables, which are rather small, are used to 
maintain topographic data tables, which may consume 
lots of disk space depending on the amount of 
topographic data to handle. Organizational and summary 
tables for the market and archive are stored always on 
the hard disk. They can be used in many cases to 
retrieve general information about the data without 
having to search in the large topographic data tables. 
While the topographic data tables of the market are also 
available permanently on the disk, they may be stored on 
external storage media for the archive. These media 
must allow for direct access like hard disks. Examples 
are magneto-optical disks or removable disk cartridges. 
Tapes can only be used for backup purposes (,disaster 
prevention"). 
5.5 Derived Products Market 
By using primary data as input to DTM application 
programs several types of products can be derived. 
Naturally the most important products are interpolated 
grids, but also calculated slope models or contour lines 
are typical derived products. A decision has to be made 
by the user, whether it is necessary to create these 
derived products and to store them permanently or it is 
more convenient to re-create them from the primary 
topographic data on demand. The answer depends 
mainly on the production environment of the user and the 
frequency of customers orders. 
Currently SCOP.TDM supports management of regular 
grid data for different data formats as well as the hybrid 
DTM structure of SCOP (Kóstli, Sigle, 1986). 
The strategies for managing derived products in the 
,Derived Products Market" are quite analogous to 
managing primary data in the ,Topographic Data 
Market“. Again organizational and summary tables are 
used to allow for answering general queries about the 
available products. But an essential difference to 
managing primary topographic data is that derived 
products are stored in the data format they have been 
created. They are not stored in TOPDB tables. This 
method has some advantages. There is not involved any 
conversion process and therefore no loss of information 
occurs. Furthermore these products can still be accessed 
by DTM application programs. Finally products can be 
managed, that are not coming directly from a SCOP 
production environment. 
The export process for derived products is much more 
complex than for exporting topographic data, because 
derived products may be stored in different data formats 
and may have different grid intervals. It is possible to 
deliver derived products according to a user specified 
area of interest and a selected grid interval in any 
requested and supported data format. All necessary 
actions for merging together individual derived products 
for the selected final product are performed 
automatically. 
A completely different problem concerning derived 
products is the updating process in the case of modified 
primary topographic data, from which the products have 
been created. Precautions have been taken to allow for 
163 
recognizing the necessity to update derived products in 
such cases. 
6. PRACTICAL EXPERIENCES 
After an experimental phase of a few months the Federal 
Office for Topography in Switzerland decided at the end 
of 1994 to integrate SCOP.TDM into their DTM 
production environment. The software system has been 
installed on a UNIX platform (RS/6000; AIX). 
Both the so-called ,Basismodell" (Basic Model), which 
consists of contourlines, lakes and spot heights derived 
from the topographic map 1:25000, and the so-called 
Matrixmodell" (Matrix Model) representing a regular grid 
with a grid interval of 25 meters are managed by 
SCOP.TDM. Primary data are stored in about 250 
topographic data tables. On an average each table 
contains about 200000 points and has a size of about 3 
MB. This organization results more from practical 
experience than from theoretical models. For storing a 
single point 18 bytes are used. The total disk space 
occupied by all the topographic data tables and the 
appropriate information and summary tables is less than 
1 GB. 
The Austrian Federal Office for Metrology and Surveying 
uses SCOP.TDM also on a UNIX system (HP9000/715; 
HP-UX). The primary data have been compiled 
photogrammetrically (profiles, breaklines, formlines, spot 
heights) and consist of about 80 millions of points. The 
size of the topographic data market is about 2.5 GB. 
REFERENCES 
IPF, 1994. The Program System SCOP. Product 
Information of the Institute for Photogrammetry and 
Remote Sensing, Vienna University of Technology, 
Vienna, Austria. 
Kóstli, A., Sigle, M., 1986. The random access data 
structure of the DTM program SCOP. In: International 
Archives of Photogrammetry and Remote Sensing, 
Edinburgh, Scotland, Vol. XXVI, Commission IV, pp. 45- 
42. 
Loitsch, J., Kraus, K., 1986. Topographic Information and 
Archiving Software (TOPIAS). In: International Archives 
of Photogrammetry and Remote Sensing, Edinburgh, 
Scotland, Vol. XXVI, Commission IV, pp. 217-227. 
Loitsch, J., Molnar, L., 1991. A Relational Database 
Management System with Topological Elements and 
Topological Operators. In: Proceedings of Spatial Data 
2000, Department of Photogrammetry and Surveying, 
University College London, pp. 260-259. 
Loitsch, J., Otepka G.,1976. A computer program for 
digitally controlled production of orthophotos. In: 
International Archives of Photogrammetry and Remote 
Sensing, Helsinki, Finland, Vol. XXI, Commission IV, pp. 
202-204. 
International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B2. Vienna 1996