Accuracy assessment of the Croatian height transformation model

The Croatian height transformation model (HTMV) enables the transformation of absolute heights of discrete points with known horizontal positions from the Trieste 1875 reference system used throughout the former Republic of Yugoslavia and in Croatia known as HVRS1875 to the new height reference system of the Republic of Croatia (HVRS71) and vice versa. The HTMV is realised as a grid transformation model based on separate modelling of datum and distortion components comprised in height differences. The quality of the transformation model is assessed by comparing the difference in height values at benchmarks that were not used in the model derivation against height differences at the benchmark locations interpolated from the model. The results indicate a high external and internal accuracy of the transformation process, which points to the adequacy of the HTMV utilisation for engineering purposes.