Experts in Remote Sensing
    and Agrometeorology



Speckle filtering in SAR images


This example illustrates the performances of the last generation of the Gamma-Gamma Maximum A Posteriori (MAP) adaptive speckle filter for SAR (Synthetic Aperture Radar) images. In this version, the second order spatial statistics are used to perform structure detection
(E. Nezry, M. Leysen, G. De Grandi, "Speckle and Scene Spatial Estimators for SAR Image Filtering and Texture Analysis", Proceedings of SPIE, Vol.2584, pp.110-120, Sept. 1995).

This enables to speed up substantially the filtering process, with a gain of about 70% in comparison to the older version
(A. Lop�s, E. Nezry, R. Touzi, H. Laur: "Structure Detection and Adaptive Speckle Filtering in SAR Images", International Journal of Remote Sensing, Vol.14, nr.9, pp.1735-1758, June 1993).

In addition, the textural properties of the imaged scene are much better preserved: textured areas covered by forest are much better identified on the filtered image, and the useful spatial resolution of the radar sensor is preserved.

 


To cope with the specific cases in which the theoretical assumptions of the Gamma-Gamma MAP filter are no longer reliable (very textured scene, scene located on strong relief), PRIVATEERS NV has developed a new adaptive speckle filter: the Gamma/Distribution-entropy MAP filter
(E. Nezry and F. Yakam Simen, 1999: "New distribution-entropy Maximum A Posteriori speckle filters for detected, complex, and polarimetric SAR data", Proceedings of IGARSS'99, Vol.3, July 1999).
With this new speckle filter, we are presently able to restore optimally the radar reflectivity and the textural properties of all possible imaged scenes.



  Software


A Speckle Filtering Module for Radar (SAR) images, including all the newest adaptive speckle filtering algorithms developed by PRIVATEERS NV, is available since 2004 withinSARscape, a most professional satellite image processing software package.

SARscape is fully compatible with the geomatics and GIS (Geographic Information System) software ®IDL-ENVI (Research Systems Inc.) and ®ArcView (ESRI Inc.).
SARscape supports Windows 98/NT/2000/XP and Linux 2.6 operating systems.

The filtering module provides different specific algorithms to process :

SARscape is produced and commercialized by the Swiss company SARMAP SA.
SARscape is a Registered Mark of SARMAP SA.