INTERACTIVE DTM DATA ACQUISITION AND VERIFICATION 
ON COMPUTER SUPPORTED ANALOGUE STEREOPLOTTERS 
Zeljko Cvijetinovié, Dragan Mihajlovié 
Institute of Geodesy, Faculty of Civil Engineering, University of Belgrade 
Bul. revolucije 73, 11000 Belgrade, Yugoslavia 
Commission IV, Working Group 4 
KEY WORDS: DEM/DTM, Software, Acquisition, Analysis, Mapping, Analogue Instruments, Surface Modelling 
ABSTRACT: 
Analogue stereoplotters are still in use in many surveying agencies all over the world. Requirements for digital data 
and performances of PC computers make it necessary and possible to upgrade these instruments into efficient 
systems for digital mapping. Low cost software solution which does not include full upgrade into analytical instrument 
is presented. The main emphasis in this paper is on the software support to interactive acquisition and verification of 
DTM data. Basic concepts, applied algorithms and the first results are described. Solution is realised as a module of 
the MapSoft software system. The MapSoft is official software in Yugoslavia for support to acquisition, processing, 
analysis, maintenance and distribution of large scaled map data. Brief description of MapSoft and basic concepts of 
technology of digital mapping called Digital Geodetic Map (DGM) are also presented. 
1. INTRODUCTION 
Survey agencies in Yugoslavia, except military ones, 
have only analogue photogrammetric instruments. 
Currently, there are very small chances that this situation 
will be much better in future. Therefore, these 
instruments are still going to play a considerable role in 
geodetic practice for a long period of time. On the other 
side, fast development of computer technology has 
provided personal computers with enough power to 
support the most demanding tasks in digital mapping. 
The result was a development of various photogram- 
metric software at the Chair for Photogrammetry and 
Cartography (Institute for Geodesy, Faculty of Civil 
Engineering Belgrade). This software is designed to 
serve as a support to analogue stereoplotter equipped 
with encoders and connected to a PC compatible 
computer under MS DOS. 
The last software product in this series is MapSoft 
(Mihajlovié, 1996). At the beginning, the MapSoft was 
primarily a software for support to interactive 
photogrammetric digital mapping. After achievement of 
this goal, modules for support to other data acquisition 
techniques and for some other applications were 
developed within the MapSoft. Therefore, support to 
photogrammetric data acquisition has become only one 
among numerous MapSoft' s functions. 
Simultaneously with the development of MapSoft, a 
constitution of the conception of Digital Geodetic Map 
(DGM) in Serbia was going on. This conception, which 
has been proclaimed in official survey regulations, 
covers a complete technology for production, 
maintenance and distribution of large scaled map 
contents in completely digital form. The basic concepts 
of the DGM and MapSoft will be included in the paper in 
more details. 
To provide complete support to DGM, some changes of 
MapSoft were necessary. At the beginning of 
development of the MapSoft, attention was paid to the 
DGM data such as: parcel boundaries, buildings, 
communications, pipes, etc. Even though every entity in 
data base contained the third coordinate, it was in 
essence only horizontal representation of objects in the 
field. For the full implementation of the DGM concept, it 
was necessary to extend MapSoft's data base with other 
height information. The application of technology of 
Digital Terrain Models (DTM) was the only solution that 
could be satisfactory. 
The applied solution is described in this paper. It is 
realised as the MapSoft's software module and it 
provides support to various techniques of DTM data 
acquisition. One of the most important is DTM 
measurement on analogue stereoplotters connected 
with PC computer. The functions for data verification are 
based on generation of TIN based DTM which serves for 
subsequent data analysis. The results of this analysis 
help operator to detect and eliminate erroneous data 
and to improve the quality of the acquired DTM by 
additional measurements. 
206 
International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B4. Vienna 1996 
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