Creating identities – two solutions for rigorous deformation analysis of areal observations in engineering geodesy

The development of areal measurement systems increased the expectations in the gain of information, also for geodetic deformation measurements. These expectations have been met, but so far by pure comparison of displaced point clouds delivering parameters of rigid-body motions. The established standard in engineering geodesy is the rigorous deformation analysis with integrated statistical significance tests. For areal deformation analysis, this has so far only been successful in rare cases and via workarounds. Among other challenges, the fundamental problem for the congruency test, namely to find point identities in point clouds across two measuring epochs, is still not solved. Especially for scanning and imaging total stations the TUM Chair of Geodesy has developed two different strategies to overcome this fundamental problem. We present one approach using additional imaging information and another method using the geometrical information only to derive point identities in dense point clouds for the rigorous congruency analysis – both suitable for statistical significance tests. Different tests in the laboratory and during real use cases prove the suitability of the approaches described. The pseudo observations to multi-temporal identities created from the scan data have the same accuracy as single point observations to signalized targets and allow to detect deformations of only a few millimeters significantly.