Local to ETRS89 datum transformation for Slovenia: triangle-based transformation using virtual tie points

Abstract

The present paper presents a geodetic datum transformation between the old and new national coordinate reference systems of Slovenia. The basis for transformation is a set of about 2000 points coordinated in both systems. Virtual tie points are used, which form a regular triangular network covering the entire country. In order to enable extrapolation, the network was expanded, thereby reducing its density. Coordinate shifts between both coordinate systems were determined using best-fit transformation in the immediate neighbourhood of each virtual tie point. Weights assigned to these points depend upon their density and distance from the virtual tie point. The results prove significant advantages of the proposed model: high accuracy, minimisation of distortions, continuity and reversibility of transformation. Therefore, the model has been chosen for transformation of all spatial databases which continuously cover the entire territory of the country and require transformation accuracy of better than one metre.