A persistent scatterer experiment using corner reflectors has been set up to validate the quality of InSAR Envisat/ERS-2 phase observations. The validation is performed by means of independent precise leveling observations of corner reflector motion in time, and comparison with respect to InSAR observables. The estimated precision of the InSAR double-differenced phase measurements is 2.8mm (vertical) for "zero-gyro" ERS-2 data and 1.6mm for Envisat. An analysis of an integration of corner reflectors and neighboring "natural" persistent scatterers is also presented.

In the PSIC4 experiment, eight different processing approaches for time series analysis of InSAR data were applied to a data set containing an unknown deformation signal. Results of the experiment showed different spatial point density for different processing approaches. The results of most of the groups that participated in the project suffer from a low spatial density of persistent scatterers in deforming areas. This lack of PS points in the area of interest raises the hypothesis of type-I errors (falsely rejected PS) due to imperfections in the mathematical model of PS processing. We investigate the contribution of three different sources of type-I errors: atmospheric phase screen (APS) and orbital errors, non-linear deformation mechanisms, and azimuthal sub-pixel position of the scatterers. We investigate these type-I errors and present significant improvements in their identification by optimization of the mathematical model, leading to an improved density of persistent scatterers.

InSAR data acquired from independent overlapping tracks can be exploited for a reliability assessment of the Persistent Scatterer InSAR (PS-InSAR) technique. Here we present a mathematical framework for the datum connection of multiple tracks, simultaneously evaluating the precision and reliability of PS-InSAR estimates. This datum connection can be subdivided in two steps. Firstly, the PS locations are converted to a common radar coordinate system: the geometry of the so-called 'master track'. The second step consists of the connection of the PS-InSAR parameter estimates (velocities, displacements, heights). Since each track has its own reference PS, the transformation is parameterized as a translation, which can be optionally extended with a trend in range and azimuth direction due to unmodeled residual effects. Multi-track datum connection has been applied in the Groningen region, the Netherlands, which is affected by subsidence due to gas extraction with displacement rates up to 7 mm/year. The main reservoir is (partly) visible in 6 independent overlapping ERS tracks (ascending and descending). Utilizing the different viewing geometries, the connected PSInSAR estimates could be further decomposed into horizontal and vertical displacement rates.

InSAR data acquired from independent overlapping tracks can be exploited for a reliability assessment of the Persistent Scatterer InSAR (PS-InSAR) technique. This is obtained by means of the datum connection of multiple tracks, simultaneously evaluating the misclosures between multi-track PS-InSAR estimates. Due to a different viewing geometry, many of the detected PS will physically not be the same. However, their estimates may still refer to the same deformation signal. The existence of independent observations of the same deformation signal provides a powerful tool to increase the redundancy and evaluate the reliability. The datum connection can be subdivided in two steps. The first step consists of the conversion of PS locations to a common datum. Secondly, the PS-InSAR parameter estimates (velocities, displacements, heights) are connected. In stead of the conventional approach of separately geocoding each track, we propose the use of a common radar datum defined by the acquisition geometry of the 'master track'. Multi-track datum connection has been applied in the Groningen region, the Netherlands, which is affected by subsidence due to gas extraction with displacement rates up to 7 mm/year. The main reservoir is (partly) visible in 6 independent overlapping ERS tracks from 1992 (ascending and descending). Datum connection resulted in a consistent set of PS-InSAR deformation estimates. Additionally, the deformation signal was decomposed in horizontal and vertical movements, utilizing the different viewing geometries of the tracks. ©2007 IEEE.