An Analysis of Insar Displacement Vector Decomposition Fallacies and the Strap-Down Solution

To retrieve the full displacement vector from InSAR, three line-of-sight (LoS) observations from different viewing geometries are required. However, often, at most two LoS observations are available. Within the literature, we encounter different approaches to address for this problem, unfortunately often with either mathematical or semantic flaws. Their impact reaches from quantitative errors in the reported studies, mismatches in comparative studies with other geodetic techniques, a lack of trust in the technology by end-users, to plain confusion. We propose both a uniform nomenclature and an alternative approach to the standard 3D decomposition problem using the concept of a strap-down reference system.