In the old coordinate system, church belfries often served as reference points in detail surveying. Consequently, their coordinates were regularly maintained in the geodetic databases of the old coordinate system. Their usability was significantly reduced by the establishment of the new coordinate system along with the use of satellite-based positioning methods and transformation models. Considering that the number of ground points of the old trigonometric geodetic networks decreases due to reconstruction, today they have gained practical value. Most of them were preserved in their original condition, which enables a continuous transition from the old to the new coordinate system as well as the reconstruction of the old situation on the basis of the old coordinate system data. They can be used in the determination of the transformation parameters of the detail or for the quality evaluation of the state transformation model. For this, their coordinates should be determined in the new coordinate system. The present article describes the determination of positions of five church belfries in the new coordinate system D96/TM, which are located in the southwestern part of Ljubljana. The procedure combines the determination of the geodetic network datum by GNSS, the inclusion of terrestrial measurements and free-network least squares adjustment and further use of the S-transformation. Further comparison of coordinates, acquired in different ways, shows some centimetre differences in each coordinate component for the given sample of church belfries. Therefore, for the sample under consideration, we can conclude that the Slovenian triangle-based transformation model effectively describes the transformation between the old and the new coordinate systems in the area under consideration.

Key words: church belfry, geodetic network, GNSS methods, terrestrial measurements, adjustment, S-transformation