Paper presented at the 25th EUREF Symposium held in Leipzig, Germany, 3–5 June 2015
National Report of Slovenia
to the EUREF 2015 Symposium in Leipzig
Klemen MEDVED1, Sandi BERK2, Božo KOLER3, Žarko KOMADINA1, Miran KUHAR3, Katja OVEN2,
Polona PAVLOVČIČ PREŠEREN3, Jurij REŽEK1, Oskar STERLE3, Bojan STOPAR3
1
Introduction
pillar is mounted on a platform that has a foundation of
three 20-meter long piles of reinforced concrete.
This paper is a review of activities regarding national
geodetic reference frames, CORS networks and activities related to EUREF in Slovenia for the period 2014–
2015. Highlighted are activities within the project called
Modernization of Spatial Data Infrastructure to Reduce
Risks and Impacts of Floods, see Režek et al. (2014). A
more comprehensive presentation of these activities was
given at the 43rd Slovenian Surveying Day, Sežana, 9–
10 April 2015, see Stopar et al. (2015).
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National Combined Geodetic Network
In the last national report, some starting activities on
establishing the so-called zero-order combined geodetic
network of Slovenia were presented (Režek et al., 2014).
By now, micro locations for the six zero-order stations
have been chosen and two of them (Kog and Prilozje)
have already been built up (Medved, 2014), see Figures
1 and 2.
Figure 2: Zero-order station of the national combined
geodetic network in Prilozje, Bela Krajina (White
Carniola).
As one of the six zero-order stations, the Koper tide
gauge station has been chosen, see Figure 3. The Koper
tide gauge station as well as the Kog seismic network
station is maintained by the Slovenian Environmental
Agency.
Figure 1: Zero-order station of the national combined
geodetic network in Kog, Štajerska (Slovenian Styria),
at the location of the seismic network station.
The Kog station was built up at the location of the
existing station of the seismic network of Slovenia, see
Figure 1. The Prilozje station was built up at the location
of the Prilozje Sport Airfield. It is a double station (equipped with two GNSS receivers), see Figure 2. The main
1
Figure 3: Zero-order station of the national combined
geodetic network in Koper – at the location of the tide
gauge station.
Surveying and Mapping Authority of the Republic of Slovenia, Zemljemerska ulica 12, SI-1000 Ljubljana, Slovenia
e-mails: {klemen.medved, zarko.komadina, jurij.rezek}@gov.si
2 Geodetic Institute of Slovenia, Jamova cesta 2, SI-1000 Ljubljana, Slovenia
e-mails: {sandi.berk, katja.oven}@gis.si
3 University of Ljubljana, Faculty of Civil and Geodetic Engineering, Jamova cesta 2, SI-1000 Ljubljana, Slovenia
e-mails: {bozo.koler, miran.kuhar, polona.pavlovcic, oskar.sterle, bojan.stopar}@fgg.uni-lj.si
The other three locations for the zero-order stations
are Areh in the Pohorje Hills, Korada in the Primorska
Region, and Šentvid pri Stični in the central Slovenia.
These stations are under construction. It is planned to
put into operation all the station infrastructure of the
combined geodetic network of Slovenia within a few
months.
About 1459 km of levelling lines were measured
between 2007 and April 2015, which is about 80% of
the total amount of the planned levelling lines. Calculation of the whole network will be performed after finishing with the last two planned levelling lines (till the end
of 2015). The average standard deviation of height differences for 1 km line is 0.42 mm (Stopar et al., 2015).
The aim of the combined geodetic network of
Slovenia is new, high quality realization of the national
terrestrial and height reference systems as parts of the
national spatial reference system. Six zero-order stations
will be operated as a CORS network. It enables to
monitor their positions in time. Some or all of the
network stations could also contribute to the European
and other international projects, such as ECGN, EPN,
EPOS, EUPOS, IGS etc. (Stopar et al., 2015).
Between September 30th and October 15th 2014,
re-measurement of the absolute gravimetric network of
Slovenia was conducted by the Austrian Federal Office
of Metrology and Surveying (Bundesamt für Eich- und
Vermessungswesen – BEV). FG5/242 absolute gravimeter was used, see Figure 4. All six absolute gravimetric stations were re-measured, i.e. Areh, Bogenšperk, Gotenica, Kluže, Sevnica, and Socerb. At least 24
hours of measuring time with ~4000 to ~6000 drops was
used for calculation of final gravity values. The drop
sigmas vary around 5 μGal for the most stable stations
and up to around 15 μGal. Comparison to the previous
results (from 1996) shows deviations between −32 μGal
for the Sevnica station and +25 μGal for the Bogenšperk
station. Vertical gradient was also measured at each
station. The relative gravity observations were performed with a Scintrex CG5 relative gravimeter (Ullrich,
2014).
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National Vertical Reference Frame and
Gravity Field
Activities regarding the national vertical reference
system have been focused on:



geometric levelling and relative gravity measurements in the newly defined high precision
levelling lines,
new absolute gravity measurements (re-measurements) in the complete absolute gravimetric
network, and
relative gravity measurements (densification) of
the relative gravimetric network needed for the
new (quasi)geoid model computation.
Figure 5: Relative gravimetric network in Slovenia and
the neighbouring countries – the current status.
Figure 6: Densification of the relative gravimetric
network points in Slovenia – plan for 2015.
Figure 4: Absolute gravity measurement at the Socerb
station, October 9th 2014.
Detailed plan of the gravimetric grid points was prepared in 2014. It provides locations of 600 new gravimetric points within a 4-km grid over central Slovenia
(~13800 km2), where the density of existing gravimetric
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points is insufficient, see Figures 5 and 6.Realization of
this plan is in progress and should be finished this year.
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New EUREF GNSS Campaign
A new EUREF GNSS campaign is planned in
Slovenia, covering a large amount of sites from the
previous campaigns (EUREF-SLOCRO-94, Slovenia95, and CROREF-96). This campaign will also include,
see Figure 7:





6 zero-order combined geodetic network stations
(under construction),
14 SIGNAL network GNSS stations,
18 permanent GNSS stations from neighbouring
countries (APOS, CROPOS, FVG, and GNSSnet.hu),
some additional geodynamic sites, and
surrounding IGS stations to fix the network.
project of verification of the transformation model was
initiated in 2014 (Berk et al., 2015). The aim of the
project was to check the quality of transformation for
cadastral dataset (cadastral boundary points), focusing
on the high-quality spatial data. Results of this pilot
project are:




methodology for the field control survey,
methodology for data processing (statistical
measures, interpretation of results),
criteria for verification of the transformation
model, and
plan for the country-wide project of verification
of the proposed transformation model.
Study area for the pilot project was the city of
Ljubljana and its surrounding countryside. For about
350 points within 10 testing areas, coordinates in
ETRS89 were obtained by GNSS measurements. These
coordinates were then compared to the official coordinates in the local CRS, which were transformed into
the ETRS89 by using the transformation model under
verification.
The country-wide project for the verification of the
old national (local) to ETRS89 datum transformation
model started at the beginning of 2015. 70 testing areas
were selected across the country, see Figure 8.
PM
PD
GR
PS
SP
Figure 7: Potential stations to be included into the
new EUREF GNSS campaign in Slovenia.
Future campaign results should provide the basis for
the further actions regarding the maintenance of the
ESRS in Slovenia. Possible scenarios for the terrestrial
component are (Stopar et al., 2015):




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consideration that there is no need for an urgent
replacement of the current realization of
ETRS89,
new realization of ETRS89 as a static geodetic
datum,
transition to a semi-dynamic geodetic datum, or
transition to a dynamic geodetic datum.
Verification of Local to ETRS89 Datum
Transformation Model
Local to ETRS89 datum transformation model for
Slovenia is based on ~2000 geodetic points with coordinates, determined in both coordinate reference
systems (hereinafter: CRS), see e.g. Medved et al.
(2010). According to the new National Land Survey
Reference System Act (Režek et al., 2014), all spatial
datasets in the country will be transformed into the new
national CRS (Slovene realization of ETRS89). To be
able to perform this transformation adequately, a pilot
DL
JP
Figure 8: Testing areas for the country-wide project
of verification of the local to ETRS89 datum
transformation model for Slovenia.
Realization of this project is in progress and should
be finished by the end of this year. For testing areas
failing the verification criteria, densification of tie points
is provided within the second phase of the project.
Finally, an improved version of the transformation
model will be generated.
Acknowledgement
Activities presented in this report were partially
supported by the EEA Financial Mechanism Programme
2009–2014 for Slovenia – SI02 (EEA Grants and
Norway Grants).
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