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Coherent vs. Persistent Scatterers: A case study.

Luca Marotti(1), Nico Adam(1), Alessandro Parizzi(1) and Konstantinos P. Papathanassiou(1)

(1) German Aerospace Center (DLR), Muenchner Strasse, 20, 82234 Wessling, Germany


Point-like scatterers play an important role in SAR applications as their deterministic response allows an evaluation of their phase information widely unaffected by speckle. The most prominent class of such point-like scatterers are the so called Persistent Scatterers (PSs) characterised by a long term temporal stability [1]. Accordingly, the identification of PSs is based on the temporal stability of their phase and/or amplitude scattering patterns and relies on the availability of large time series of acquisitions. Their introduction in SAR interferometry enabled the development of deformation monitoring applications by measuring the Line-of-Sight displacement.

More recently, another class of point-like scatterers has been introduced, namely the Coherent Scatterers (CSs) [2]. Their detection is based on their spectral correlation properties and has been addressed in terms of image sub-look (spectral) correlation. Thus, it can be performed even on the basis of a single SAR image as long as the system bandwidth is large enough. The (amount of) spectral correlation of a scatterer is linked with its nature and CSs have been explored mainly in terms of their polarimetric properties that have been used to characterise the individual CSs and to extract information about dielectric properties and physical orientation. The temporal stability of CSs do not necessarily requires a stable scattering behavior as long as the deterministic nature of the CSs is not changing.

Towards the combination of the information provided by the two concepts, the question about the temporal stability of CSs has to be answered. First investigations of the temporal behaviour of CSs have been performed on the basis of Quad-pol data acquired at L-band by JAXA’s ALOS/PalSAR [3]. However the lack of sufficient acquisitions does not allow the implementation of PSs detection by means of ALOS/PalSAR. In order to investigate this missing point we propose to evaluate the relationship of CS’s and PSs based on image time series. Data processes by DLR’s persistent scatterer system PSI-GENESIS are used for this reason. The temporal stability of the CSs and the spectral properties of the PSs are evaluated and conclusions about improved detection schemes are discussed.

[1] A. Ferreti, C. Prati & F. Rocca, “Permanent scatterers in SAR interferometry,” IEEE Transactions on Geoscience and Remote Sensing, vol. 39, no. 1, pp. 8-20, January 2001.

[2] R.Z. Schneider, K.P. Papathanassiou, I. Hajnsek & A. Moreira, “Polarimetric and Interferometric Characterization of Coherent Scatterers in Urban Areas”, IEEE Trans. Geoscience and Remote Sensing, vol. 44, No. 4, pp. 971-984, April 2006.

[3] L. Marotti, R.Z. Schneider & K.P. Papathanassiou, ”Coherent Scatterers (CSs) Detection and Characterization with ALOS-PalSAR”,. in 3rd Intl. Workshop on SAR Polarimetry and Polarimetric Interferometry (PolInSAR2007), Frascati, Italy, 22-26 January 2007.


Workshop presentation

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