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<< Click to Display Table of Contents >> Gamma and Gaussian Filtering - Polarimetric - Wishart Gamma DE MAP |
  
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<< Click to Display Table of Contents >> Gamma and Gaussian Filtering - Polarimetric - Wishart Gamma DE MAP |
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Purpose
Polarimetric data can be filtered using any of the following procedures:
| - | Wishart Gamma MAP. |
| - | Wishart DE MAP. |
Optimal results can be achieved by selecting the appropriate filter depending on the land morphology and scene texture, this last to be considered also in relationship with the data spatial resolution.
Technical Note
Wishart Distribution-Entropy MAP (Wishart DE MAP)
It is suitable for fully polarimetric (single-look or multi-look, complex) SAR data. It is best performing in presence of strong mixed texture or strong relief.
Input Files
Input HH File
Input file name of Single Look Complex (_slc) data for the HH channel. This file is mandatory.
Input VV File
Input file name of Single Look Complex (_slc) data for the VV channel. This file is mandatory.
Input HV VH File
Input file name of Single Look Complex (_slc) data for either the HV or VH channel. This file is mandatory.
Parameters - Principal Parameters
Window Size in Azimuth and Range
Filter window size (use of square windows is suggested). The signal samples to be used for the computation of the local statistics are collected within a neighborhood where the autocorrelation function of the radar reflectivity is meaningful, in order to avoid taking samples within areas of a different nature than the pixel under process. In practice, this means that signal samples will not be collected farther than a certain distance - the de-correlation length - from the pixel under process.
Equivalent Number of Looks (ENL)
The Equivalent Number of Looks is equivalent to the number of independent Intensity values averaged per pixel during the multi-looking process. This parameter can be easily estimated over a homogeneous (stationary) sample in in the input Intensity data according to:
ENL = mean2 / standard deviation2
In case that ENL is not set, the software tries to retrieve it automatically; if it fails it takes the Number of Looks (NL) used during the multi-looking process is considered.
Note that, to tune the strength of speckle filtering and the level of preservation of scene details, it is preferable to adjust the value of the ENL, rather than to change the size of the processing window:
| - | To reduce the strength of speckle filtering, with the aim to preserve the thinnest details of the scene, enter a ENL value slightly higher than the calculated one. |
| - | Inversely, to improve the filtering of the speckle (possibly at the cost of the thinnest details of the scene...), enter a ENL value slightly lower than the calculated one. |
Span Equivalent Looks
The equivalent number of looks of the Span image (HH+VV+2.HV) is usually set as two times the ENL.
Azimuth Looks
Azimuth number of looks for the output products.
Range Looks
Azimuth number of looks for the output products.
Grid Size for Suggested Looks
The grid size, in meters, used to tune range and azimuth looks. If the other parameters are manually set, the grid size will not imply a change in their values.
Parameters - Global
It brings to the general section of the Preferences parameters. Any modified value will be used and stored for further processing sessions.
Parameters - Other Parameters
It brings to the general section of the Preferences parameters. Any modified value will be used and stored for further processing sessions.
Output Files
Output HH File
Output file name of the filtered (possibly multi-looked) Intensity data for the HH channel. This file is mandatory.
Output VV File
Output file name of the filtered (possibly multi-looked) Intensity data for the VV channel. This file is mandatory.
Output HV VH File
Output file name of the filtered (possibly multi-looked) Intensity data for either the HV or the VH channel. This file is mandatory.
_fil
Filtered data (HH, VV, and HV or VH) and associated header files (.sml, .hdr).
_fil_polv_...
Filtered Polarimetric Vector / Polarimetric Covariance Matrix and associated header files (.sml, .hdr). These are:
-Shh.Shh*
-Svv.Svv*
-Shv.Shv*
-Re{Shh.Svv*}
-Im{Shh.Svv*}
-Re{Shh.Shv*}
-Im{Shh.Shv*}
-Re{Svv.Shv*}
-Im{Svv.Shv*}
_slc_span
Filtered “Span“ image - where Span = (HH+VV+2.HV) - and associated header files (.sml, .hdr).
_rgb.tif
Multi polarization RGB composite - where HH, HV and VV are respectively in Red, Green and Blue - and corresponding header file (.sml).
Details specific to the Units of Measure and Nomenclature of the output products can be found in the Data Format section.
General Functions
Exec
The processing step is executed.
Store Batch
The processing step is stored in the batch list. The Batch Browser button allows to load the batch processing list.
Close
The window will be closed.
Help
Specific help document section.
Specific Function(s)
None.
Task, SARscapeBatch object, SARscapeBatch script example
References A. Lopes, S. Goze and E. Nezry: "Polarimetric speckle filters for SAR data". Proceedings of IGARSS'92 Symposium, 1992. Lopes A., E. Nezry, R. Touzi, and H. Laur: "Structure detection and statistical adaptive speckle filtering in SAR images". International Journal of Remote Sensing, Vol. 14, 1993. E. Nezry, M. Leysen, and G. De Grandi: "Speckle and scene spatial statistical estimators for SAR image filtering and texture analysis: some applications to agriculture, forestry, and point targets detection". Proceedings of SPE, Vol. 2584, 1995. Lopes A., J. Bruniquel, F. Sery, and E. Nezry: "Optimal Bayesian texture estimation for speckle filtering of detected and polarimetric data". Proceedings of IGARSS’97 Symposium, 1997. E. Nezry and F. Yakam Simen: "New distribution-entropy Maximum A Posteriori speckle filters for detected, complex, and polarimetric SAR data". Proceedings of IGARSS'99 Symposium, 1999. Nezry E. and F. Yakam Simen: "A family of distribution-entropy MAP speckle filters for polarimetric SAR data, and for single or multi-channel detected and complex SAR images". Proceedings of the CEOS SAR Workshop, ESA SP-450, 1999. Nezry E., F. Yakam Simen, F. Zagolsky, and I. Supit: "On the preservation of polarimetric signatures and polarimetric texture signatures by fully polarimetric MAP filters". Proceedings of IGARSS’99 Symposium, 1999. E. Nezry: ''Adaptive Speckle Filtering in Radar Imagery'' from the edited volume Land Applications of Radar Remote Sensin Edited by F. Holecz, P. Pasquali, N. Milisavljevic and D. Closson, 2014.