A stability analysis of the lambda estimator for solving the ambiguity problem in persistent scatterer interferometry

Persistent Scatterer Interferometry is a well-known technique to obtain displacement rates in urban areas from a stack of SAR interferograms. Besides the original method introduced by A. Ferretti, C. Prati and F. Rocca in the late 1990´s, which estimates the displacement rates and DEM corrections by an ensemble coherence maximization approach (periodogram) based on a common master image, several other algorithms have been introduced in the past few years. One of these approaches has been developed at DLR It incorporates the Least-squares AMBiguity Decorrelation Adjustment (LAMBDA) method that was originally developed for fast GPS double difference ambiguity estimation. In this paper different parameters are tested to investigate robustness and performance of this estimation method. At first the effects of a reduced number of observations and varying reference points on the estimation with LAMBDA are analyzed while in the second part a direct comparison between LAMBDA and ensemble coherence maximization (periodogram) is performed.