Experts in Remote Sensing
    and Agrometeorology



Polarimetric SAR images


This example illustrates the performances of a fully polarimetric speckle filter: the Wishart-Gamma Maximum A Posteriori (MAP) adaptive speckle filter for polarimetric SAR images
(A. Lopès, S. Goze and E. Nezry: "Polarimetric Speckle Filters for SAR Data", Proceedings of IGARSS'92, Vol.1, pp.80-82, May 1992).

In this version, detectors for edges, linear structures and point targets are associated to the polarimetric filtering process
(E. Nezry, A. Lopès and R. Touzi: "Detection of structural and textural features for SAR images filtering", Proceedings of IGARSS'91, Vol.4, pp.2169-2172, June 1991).


Original data © JPL 1989; Processed image © PRIVATEERS NV 1996

The upper image is a 4-looks JPL-AIRSAR high resolution airborne polarimetric SAR image (Jet Propulsion Laboratory, Pasadena, CA, USA), P-band, polarizations HH (green), HV (red) and VV (blue). The imaged scene is located in the Landes pine forest, in southwest France.
The bottom image is the filtered one. Speckle is efficiently removed on all three HH, HV, and VV channels, without loss in the useful spatial resolution of the radar sensor.
The textural properties of the imaged scene are well restored on all three polarimetric channels, as it is visible within the forest stands which are much better identified on the filtered image.


To cope with the specific cases in which the theoretical assumptions of the Wishart-Gamma MAP filter are no longer reliable (very textured scene, scene located on strong relief), PRIVATEERS NV has developed a new fully polarimetric adaptive speckle filter: the Wishart/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 polarimetric filter, we are presently able to restore optimally the radar reflectivity and the textural properties of all possible imaged scenes
(E. Nezry and F. Yakam Simen, 1999: "On the preservation of polarimetric signatures and polarimetric texture signatures by fully polarimetric MAP filters", Proceedings of IGARSS'99, Vol.3, July 1999).
Application of the Wishart/Distribution-Entropy MAP polarimetric filter to spaceborne ALOS PALSAR polarimetric radar data is illustrated below:


Original unfiltered data (left) © JAXA 2006; Processed image (Wishart/Distribution-Entropy MAP; right) © PRIVATEERS NV 2006
HH, VV and HH polarizations are represented in red, green, and blue.


HH-VV, HH-HV and VV-HV degrees of coherence are represented in red, green, and blue.
(unfiltered data: left; Wishart/Distribution-Entropy MAP filtered; right)


Retrieval of forest biomass and standing timber volume




  Software


Adaptive speckle filtering (ERS) 2001 A Speckle Filtering Module for Radar (SAR) images, including all the newest adaptive speckle filtering algorithms developed by PRIVATEERS NV, is available since 2004 within SARscape, 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.