With the results of two measurement epochs a deformation analysis can be performed to determine the individual shifts.
Core of the analysis is a global congruency test to uncover significant misclosures within the reference points. The test considers the full cofactor matrix of both epochs. If the cofactor matrices are missing or only the point precisions are available, an approximate analysis can be carried out.
The shifted points are determined by forward- and/or backward strategy
- Backward strategy means, that be shifted points successively are removed from the group of reference points until the remaining reference points donot show misclosures any more.
- The forward strategy starts with stable reference points. Points are added successively to the group of reference points until significant misclosures occur. Before using the forward strategy the reference points are tested if they are actually stable (backward strategy!).
For monitoring buildings a two-step analysis is possible.The network is divided in reference and object points. On the basis of the recognized as stable reference points (backward strategy) the misclosures of the object points are individually tested for significance.