150 
The first two solutions are relative geoids, while the third 
solution is absolute one. For the absolute orientation almost 90 
GPS stations were used. Orthometric heights of these points 
were determined by geometric levelling. Figure 2 shows the 
latest solution from 1999. 
The influence of of the actual relief of the Earth's surface on the 
geoid forms is clearly visible on the figure; see for instance its 
raising under the Alps or its decline in the Adriatic sea. The 
Figure 2: Astrogeodetic geoid in Slovenia (solution from 1999) 
Speaking about the geoid we would like to outline some major 
facts about the situation of gravimetry in Slovenia 
Till 1991 the most work on gravimetry was in the competency 
of the Military Geographic Institute (MG1) in Belgrade. 
Gravimetric surveys for the establishment of network were 
performed by MGI and the Geological Survey of Slovenia. For 
the last ten years they had no activities beacuse of out-of-date 
equipment and no interest. In 1991 the situation in gravimetry in 
Slovenia was as followed: about 50 gravity points with 
unhomogenous disposition and rather low accuracy. 
Since 1995 Surveying and Mapping Authority of Republic of 
Slovenia (SMARS) put a lot of efforts in revitalizing 
gravimetric activités in Slovenia. In 1997 SMARS prepared a 
project of absolute gravity measurements in Slovenia. The 
project of absolute gravity measurements in Slovenia was 
organized by the International Gravity Commission, Slovenian 
Union of Geodesy and Geophysics and Surveying and Mapping 
Authority of Republic of Slovenia. Six stations were stabilized: 
castle Bogensperk near town Litija, Gotenica near town 
Ribnica, church Sv. Areh on mountain Pohorje, castle Sevniski 
grad near town Sevnica, castle Socerb near Koper and fortress 
Kluze near Bovec. 
Because of the rather bad situation of the gravity investigations 
in Slovenia, activités in this field should be started from the 
begining. The network of absolute gravity points will be the 
base for the further development of gravity network. There are 
plans of establishment of a new fundamental gravity network 
for the whole country. 
SLOVENIA AND EUREF 
The development of a new reference coordinate system in 
Slovenia that should comply all the needs of the contemporary 
geodesy regarding state and unified European coordinate 
maximum varitation of the calculated geoid heights is 5.7m 
(Figure 2) 
For the time being there is no local gravimetric solution for the 
geoid. But, gravity anomalies from territory of Slovenia were 
used in the computation of European Gravimetric Geoid 1997 
(EGG97), (Denker et al., 1997). Figure 3 shows the differences 
between gravimetric geoid and aforementioned astrogeodetic 
solution (gravimetric undulations were transformed to Slovenian 
height system). 
Figure 3: Differences between astrogeodetic solution and 
EGG97 
system, started with the connection of the first order horizontal 
network of Slovenia with the EUREF. This connection is based 
on GPS observation campaigns performed in 1994 and 1995. 
Both campaigns were performed with the substantial 
contribution of the Institut für Angewandte Geodäsie, Frankfurt 
(now Bundesamt für Kartographie and Geodäsie) to the 
Surveying and Mapping Authority of the Republic of Slovenia. 
The EUREF-CRO-SLOV '94 GPS observation campaign was 
performed at 8 first order points (among theese were 5 points 
choosen as "real" EUREF points) during the 5 days of 
permanent GPS observations. The results were published in 
1995 (Altineret al., 1998). 
The purpose of the second EUREF campaign at the territory of 
Slovenia, under the name SLOVENIA '95 Campaign, was to 
density the existing EUREF points at the territory of Slovenia. 
Slovenia is placed in tectonical and seismological active part of 
Europe and Surveying and Mapping Authority of Slovenia 
wanted to connect the project of the establishment of new 
reference coordinate system with the monitoring the strain 
accumulation in south-eastern part of the Alps region and in the 
northern part of the Adriatic Plate. The second observation 
campaign in 1995 was performed at all 34 (35) first order 
points, at 2 stations of the triangulation base lines network 
(Bukovec and Radovljica) included in the first order network; at 
1 second order point, and at 12 geodynamic points. GPS 
observation were carried out for six days, in two blocks with 3 
day of 24 hours of observations each. The final coordinates of 
the Slovenia '95 Campaign are given in the ITRF93 epoch 
1995.7, respectively in the ETRS 89 epoch 1989.0. Unweighted 
RMS values with respect to the combined solutions are 2 mm in 
north direction, 2 mm in east direction and 6 mm in height 
direction. At the moment became availble also the common 
solution of the three GPS observation Campaign performed at 
the territory of Slovenia and the surrounding area (Y. Altiner et 
al., 1998). Namely in 1996 there was another GPS observation 
campaign CROREF-CRODYN '96, with the duration of 15