The systematic analysis of the transformation between the German geodetic reference system (DHDN, DHHN) and the ETRF system (DREF91)

The 69 colocated sites in the area of the West Germany are used to estimate the transformation parameters with the seven parameter similarity transfor mation model. According to the solutions of transformation parameters and c orresponding residuals between DHDN and ETRF, detail analyses for global an d regional transformation are performed, which show that the global accurac y of the transformation between DHDN and ETRF is +/- 5 m with WRMS (weighte d root mean square) of +/-0.64 m and regional transformations have much bet ter fitting. Through the comparisons of estimated parameters of each state, the systematic differences in definition and observation among regional sy stems of DHDN have been confirmed. Practical usage of 7 parameter similarit y transformation and some suggestions are pointed out.