154 
CONCLUSION 
As has been seen official coordinate system in Slovenia is based 
on the old astrogeodetic network. The inherent errors and 
distorsions make it unsuitable for today's requirements which 
not only include national mapping and recording for local 
authorities and public utilities, but also scientific and safety 
purposes such as earthquake prediction, crustal dynamics and 
land subsidence. At the same time it is the twodimensional 
network. The accurate third component - height could be 
retrieved only with geometric levelling which is the base of the 
separate height network. 
Now, with the advent of GPS technology, it is becoming of 
increasing importance that such control networks be realised in 
terms of a stable and consistent coordinate frame which is of a 
global nature. The importance of a uniform and homogeneous 
coordinate reference system has become apparent in recent 
years. In Slovenia (like in most other countries) we are 
developing Geographical Information Systems and digitised 
cartographic databases which require a national and, for some 
applications, an international reference system. There are also 
needs for a coordinate reference system which encompasses not 
only the land but also the sea and air masses (international 
requirements for navigation are perhaps the best examples). 
Networks observed by GPS are becoming bigger, covering 
larger extents of the Earth's surface and are being observed 
more frequently and easily than in previous years. 
Consideration of the coordinate system, or more particularly the 
coordinate frame is of paramount importance. Ultimately, the 
coordinate frame which is adopted will define the potential 
usefulness of an observed network in future years. The frame 
must therefore be maintained over time and must be used 
consistently in a coherent manner for the processing of GPS 
data at the present and in future epochs. Establishing control 
today is most likely to be done by GPS. Whether it is re 
coordinating existing marks, establishing new stations where 
they are needed (densifying) or extending networks into new 
regions or countries, it is not difficult to show that GPS has the 
ability to perform precise surveying for geodetic purposes in a 
fraction of the time and cost than was required previously by 
terrestrial methods. With commercially available GPS receivers, 
good quality post-processing software and the routine 
production of satellite orbits, GPS campaigns can achieve a 
relative positional accuracy of better than ±0.1 ppm. However, 
this achievable precision can only be utilised if the new GPS 
network is tied or fitted to existing stations in a coherent 
manner. 
In order to be able to use ellipsoidal (GPS) heights (because 
they have no pracictal meaning) very accurate geoid models 
should be present. In order to determine such accurate models, 
gravimetric and astronomic measurements should be performed. 
Once a cm-geoid is reality, GPS technology could be easily 
utilized for height determination. 
In all its aspects Slovenia should adopt new, modern coordinate 
system, which could be used not only in surveying and mapping 
but in all related geosciences i.e. whereever location of a point 
in threedimensional even fourdimensional (considering time) 
space is needed. 
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