The Empirical Comparison of Coordinate Transformation Models and Distortion Modeling Methods Based on a Case Study of Croatia

Several coordinate transformation models enable performing of the coordinate transformations between the historical astro-geodetic datums, which were utilized before the GNSS (Global Navigation Satellite System) technologies were developed, and datums related to the International Terrestrial Reference System (ITRS), which today are most often used to determine the position. The decision on the most appropriate coordinate transformation model is influenced by many factors, such as: required accuracy, available computational resources, possibility of the model application regarding the size and shape of the territory, coordinate distortion that very often exist in historical astro-geodetic datums, etc. This study is based on the geodetic data of the Republic of Croatia in both, historical and ITRS-related datum. It investigates different transformation models, including conformal Molodensky 3 parameters (p) and 5p (standard and abridged) transformation models, 7p transformation models (Bursa-Wolf and Molodensky-Badekas model), Affine transformation models (8p, 9p, 12p), and Multiple Regression Equation approach. Besides, it investigates the 7p, 8p, 9p, and 12p transformation models extended with distortion modeling, and the grid based only transformation model (NTv2 model). Furthermore, several distortion modeling methods were used to produce various models of distortion shifts in different resolutions. Thereafter, their performance and the performance of the transformation models was evaluated using summary statistics derived from the remained positional residuals that were computed for the independent control spatial data set. Lastly, the most appropriate method(s) of distortion modeling and most appropriate coordinate transformation model(s) were defined regarding the required accuracy for the Croatian case.