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Terrafirma Validation Experiment - the Alkmaar/Amsterdam Case

Sterre Dortland(1), Freek J. van Leijen(2), Chris N. Bremmer(1) and Ramon F. Hanssen(2)

(1) TNO – Built Environment and Geoscience, P.O. Box 80015, 3508 TA Utrecht, Netherlands
(2) Delft University of Technology, Kluyverweg 1, 2629 HS Delft, Netherlands

Abstract

As part of the Terrafirma Validation Experiment, a close comparison of PS-InSAR with in-situ measurements has been done. Two test sites have been chosen in the Netherlands: (1) the trajectory of a to be built subway line in the centre of Amsterdam, and (2) the area around the city of Alkmaar, prone to subsidence due to gas extraction.

Currently, a new subway line is being built in the centre of Amsterdam. In order to assess any damage and being able to monitor any displacements a very dense monitoring network has been set up for 1500 constructions along the trajectory of this subway in 2001. The system measures x,y,z – displacement of individual prisms using robotic tacheometers. Current measurement frequency is about 1 measurement every 4 hours. This offers the possibility of comparing PS-InSAR-data closely coregistered in time and space with actual in-situ data.

The coastal area near Alkmaar in the Netherlands is rich of natural gas resources. Extraction of these resources has resulted in subsidence. The maximum deformation rate is in the order of a few millimeters per year. So far, the subsidence has been measured by conventional leveling. This test-case offers the possibility to assess PS-InSAR for a situation concerning spatially extended subsidence.

Within the framework of the Terrafirma validation project both areas are analyzed by Persistent Scatterer Interferometry (PS-InSAR). The results are analyzed and compared with the in-situ data. The results of this comparison and methodologies applied will be presented.

 

Keywords: ESA European Space Agency - Agence spatiale europeenne, observation de la terre, earth observation, satellite remote sensing, teledetection, geophysique, altimetrie, radar, chimique atmospherique, geophysics, altimetry, radar, atmospheric chemistry