GeoTeX: A GENERAL POINT DETERMINATION SYSTEM 
I.Colomina, J.Navarro and A.Térmens 
Institut Cartogràfic de Catalunya 
Spain 
ABSTRACT: 
The GeoTeX system of the Institut Cartogràfic de Catalunya (ICC) is a general geodetic and photogrammetric 
point determination system which is able to deal with any type of geometric functional model. GeoTeX is 
suited for research as well as for production purposes and can be easily extended to incorporate new models. 
Examples of tasks that the system can master are: spatial triangulation —SPOT images—, aerial triangulation 
with kinematic GPS derived positions, conventional geodetic network adjustment, DTM surface information 
and combinations thereof. In the paper, two components of the system are described: the discrete model kernel 
based on discrete mathematical techniques and the I/O kernel based on a general formal geodetic model and 
its associated formal grammar based interface language. 
KEY WORDS: abstract data types, combined adjustment, compiler-compilers, data standards, grammars, 
network discrete models. 
1 INTRODUCTION 
In a sense, network point determination is an old- 
fashioned topic in photogrammetry and geodesy. It 
can be stated at least that the subject is no longer 
appealing to the academic research community. 
On the other hand, fast, accurate and reliable point 
determination is still a must for private companies 
and official agencies in the allied fields of geodetic sur- 
veying, photogrammetry and remote sensing. These 
organizations face a variety of problems ranging from 
huge data sets, to changing hardware/software envi- 
ronments, to the extension of the traditionally sup- 
ported observable types (for instance the testing of 
new mathematical models or the use of new sensor 
types). As a consequence, remarkable efforts are still 
being made mainly by instrument /software manufac- 
turers and by research/development departments in 
land surveying agencies in order to improve and keep 
the software systems for point determination up to 
date. 
Two additional introductory remarks are in order 
here. First of all, the principles and concepts estab- 
lished by the research activities related to the for- 
mer ISPRS Working Group III.1 (period: 1984-1988; 
subject: accuracy aspects of combined point deter- 
mination) have not been transferred to practice with 
the exception of industrial photogrammetry and GPS 
aided aerial triangulation. Secondly, advantage of 
already existing progress in computer hardware and 
software must not only be taken to speed up the old 
software but also to develop superior methods and 
procedures. 
At the ICC, besides the above general remarks, 
there are particular motivations behind the research 
and developments reported in this paper. À unique 
point determination system both suited for research 
and production was needed since the development 
656 
and maintenance of two different systems cannot be 
afforded. Similarly, it is not cost feasible to develop 
and maintain a system for geodetic networks, a sys- 
tem for aerial triangulation and a system for spatial 
triangulation. 
The authors claim that this kind of a contradic- 
tion between research/production software and tai- 
lored/general software can be overcome if proper 
mathematical and computer science tools are used. 
Another claim is that the benefits of this global ap- 
proach are not solely of interest to small groups. They 
are: a cost reduction in software development, ac- 
quisition and maintenance; a closer collaboration be- 
tween teams traditionally involved —as well as tra- 
ditionally separated— in point determination tasks; 
and the introduction of factors of rationality and 
coherence in the corresponding point determination 
projects. 
2 ON GENERALITY, ADAPTABILITY 
AND PORTABILITY 
In the context of point determination systems, gen- 
erality is the power of mastering a broad range of 
[network] observations, conditions and parameters; 
adaptability is the power to incorporate new ones; 
and portability, as everywhere else, is the power to 
run on different platforms with minor or no changes, 
To say that generality, adaptability and portability 
are desirable properties of a software system is com- 
mon place. Rather than restating this, this section 
aims at describing a specific example of how the pur- 
suing of those properties has lead to certain design 
concepts. 
fe 
né 
re 
pi 
pe 
fe 
sic 
CO 
og 
du 
tr) 
ge 
sti 
Sul 
rea 
ple 
tio 
mu 
ser 
def 
prc 
vat 
DI 
2.2 
Sor 
exh 
men 
prof