At Vero Eos Et Accusamus Et Iusto Odio Dignissimos Ducimus Qui Blanditiis Praesentium Voluptatum
Mapping Ground Displacements on Wide Areas using Persistent Scatterer Interferometry
Alessandro Parizzi1, Nico Adam1 , Fernando Rodriguez Gonzalez1 , Werner Liebhart2,
Ramon Brcic1 , Xiao Ying Cong2
1 German Aerospace Center (DLR), Remote Sensing Technology Institute, Oberpfaffenhofen, 82234 Weßling, @dlr.de
2 TU München, Arcistrasse 21, 80333 München, Germany
In the recent years, the Persistent Scatterer Interferometry (PSI) (Ferretti et al. 2001) has widely demonstrated its potential in mapping ground deformation. However, the application of this technique is typically limited at the moment to areas up to 40 x 40 Km e.g. cities affected by subsidence or instable slopes. Recently, the thematic Wide Area Products (WAP) have been introduced in the framework of ESA’s Terrafirma Project (Adam et al. 2009) and a more global mapping has been newly developed. The development of the WAP is a challenge due to the following reasons:
- Low PS density (measurement points)
- Difficult spatial error propagation
- Amplification of artefacts that were hidden or partially hidden before. (e.g. effects of satellite orbiterrors)
- Automatic i.e. operator free processing
- Stronger Atmospheric noise.
- Increased computational effort.
In order to cope with these difficulties, the standard methods for the PSI processing have been reviewed and re-designed in a more operational context.
The WAP consists of numerous PSI stacks (called frames), each of them covering an area of about 100 km by 100 km for the ERS sensor. Since the quality and quantity of PSs is spatially very inhomogeneous, it is advantageous to partition each of the PSI frames into blocks with a size of about 8 km by 8 km. A robust estimation is performed in each block (Liebhart W. et al.), handling the different local qualities of the PSs. Moreover, this strategy optimizes the resources and is a scalable approach. In the developed operational system, the processing is performed in four steps which are related to hierarchical spatial levels. Firstly the best phase stable PS candidates are detected. Secondly a network is estimated independently in each of the blocks. Thirdly the networks of the blocks are merged together into a full frame network and fourthly the frames are mosaiked into a final WAP.
Figure 1: Deformation of WAP north Germany.
In order to validate the new processing capabilities, several Wide Area Products have been generated addressing different types of geohazard thematics, such like flood defense (Figure 1) and tectonics, covering areas from 20.000 Km² up to 65.000 Km².
References
Ferretti, A. et al.(2001): Permanent scatterers in SAR interferometry IEEE Trans. Geosci. Remote Sens., vol. 39, no. 1, pp. 8–20, Jan. 2001.
Adam, N. et al. (2009): Practical persistent scatterer processing validation in the course of theTerrafirma project. Journal of Applied Geophysics 69 (2009) 59–65
Liebhart, W. et al. (2012): Four Level Least Square Adjustments in Permanent Scatterers Interferometry for the Wide Area Product ,in Proc. of IGARSS 2012, Munich, Germany, July 2012