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PRODUCTION OF COUNTRY WIDE DTM FOR SERBIA AND MONTENEGRO 
S A i . a+ . i 
Z. Cvijetinovic"', S. Tomic^, M. Vojinovic? 
“ Faculty of Civil Engineering, University of Belgrade, Serbia and Montenegro, (zeljkoc, milosv)@grf.bg.ac.yu 
? Military Geographic Institute, Mije Kovacevica 5, Belgrade, Serbia and Montenegro, tomicvgi@yahoo.co.uk 
Commission IV, WG IV/7 
KEY WORDS: DEM/DTM, GIS, Mapping, Production, National, Surface, Reconstruction, Algorithms 
ABSTRACT: 
Project of building country wide DTM for Serbia and Montenegro is coming to its final phase. The project is based on scanning 
and vectorization of contours from existing 1:25000 topographic maps. Supplementing contour data with additional data sets 
available on map layers, such as hydrography and spot heights, is also planned within the project. Procedures and software tools 
for data acquisition, verification and processing were developed and implemented. Special attention was dedicated to the problem 
of high quality terrain surface modeling using contour data and all the other available information. The main concern was 
reconstruction and usage of all implicit information contained in contour data. Procedures based on TIN data structure were 
designed and implemented. Also, procedures and initial tests for the evaluation of the DTM quality are designed and started within 
the project. The paper reviews applied procedures, algorithms, current project status and some results. 
1. INTRODUCTION 
A project of establishment of completely digital production, 
maintenance, and usage of official topographic maps at scale 
1:25000 has started in Serbia and Montenegro in 2002. One of 
the key components within this project was the production of 
the corresponding DTM for the whole state territory. 
The resources for the realization of this project were rather 
limited. Solution was to use existing hardware, software and 
human resources as much as possible, and to develop solutions 
that will be tailored according to these resources. So, despite 
the recent developments of very efficient and cost effective 
systems for country wide DTM data acquisition such as INSAR 
and LiDAR, it has been decided to utilize already available 
data, because this approach required the minimum of initial 
investments. 
Data that were already available were in a form of contour 
lines with additional spot heights, hydrography and terrain 
forms. Contour lines were directly plotted from stereo pairs 
mostly by using analog photogrammetric plotters. Map layers 
containing height data were scanned together with all the other 
map layers within a single campaign. Contours were digitized 
by using semi automatic digitization i.e. line following method. 
Software functions were developed for data verification and 
easy error detection and data editing. Various tools for data 
visualization and data editing were developed, including 3D 
visualization of large DTMs by using OpenGL. 
Special attention was dedicated to the problem of surface 
reconstruction using contour data as a primary data form. The 
aim was to use all of the information contained in contour data 
implicitly. TIN based DTM modeling has been chosen. Some 
standard problems related to surface reconstruction using 
contour data are addressed. One of these is automatic detection 
  
Corresponding author 
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of structure terrain lines. Also, special method for calculation 
of terrain normals at contour points is also implemented. The 
result was a high quality terrain surface reconstruction using 
TIN data structure. The developed software tools also contain 
all other DTM analysis functions useful for data verification 
and editing. 
. Procedures were designed and some tests were made in order 
to estimate the overall quality of the acquired DTM. 
2. AVAILABLE DATA FOR PROJECT REALIZATION 
Total area of the Serbia and Montenegro is 102350km/. There 
have been some sporadic attempts to build country wide DTM 
for this area in the past, but the results were very questionable 
in terms of applied procedures and achieved quality. 
Besides maps at 1:25000 scale, there were also some other data 
available that could be used for building country wide DTM. 
One of these sources is maps in 1:5000 scale. The other is 
DTMs acquired within orthophoto projects, also for 1:5000 
mapping scale. However, these sources were not used for this 
project. The reason was that maps 1:5000 were only available 
for 4096 of the state territory, mostly for the Vojvodina and 
some larger cities, and orthophoto projects were realized only 
for some larger cities. Since there were about 6500 map sheets 
in 1:5000 scale available, it is estimated that converting these 
maps to digital form would take too much time and resources. 
The ownership was also one of the issues. Of course, these 
data sources should be considered for updating DTM from 
1:25000 maps later on. 
There are 864 7.5'x7.5' map sheets in 1:25000 scale covering 
the whole Serbia and Montenegro. Each map is composed of 
set of layers made on transparent material. These layers are the