Practical persistent scatterer processing validation in the course of the Terrafirma project

Terrafirma is an ESA project and a service element in the framework of the Global Monitoring for Environment and Security (GMES) service element programme. Based on the Persistent Scatterer Interferometry (PSI), the project provides a Pan European ground motion hazard information service. The motion monitoring is supplied by commercial companies which act as Operational Service Providers (OSPs). A Product Validation Workgroup (PVW) has been formed for the validation of the motion data products. At the moment, four OSPs operate processing chains for the generation of the basic level 1 product. These take part in a special validation project which intends to demonstrate reliability and accuracy of the PSI motion monitoring. Two independent and complementary strategies for the validation are foreseen in the validation project in order to drive sustainability. On the one hand, the Product Validation utilizes available ground truth information for the validation and assesses the final geocoded motion data. On the other hand, the Process Validation is a new type of PSI validation and compares the intermediate data in slant range regarding a reference processing and consequently avoids the problems resulting from the geocoding. This newly developed validation approach and the results of the assessment are presented. Essentially, the Process Validation experimentally provides the actual estimation performance for a typical PSI processing based on ERS or Envisat/ASAR stacks. In principle, the lower bound for the deformation deviation an end user can expect ordering a test site processing from different OSPs is reported.