PSBOXCAR

Description

PSBOXCAR applies a boxcar filter to any detected or complex-valued SAR data set. It is used commonly to increase the effective number of looks (ENL) in single-look or multi-look SAR data. PSBOXCAR reduces the speckle inherent to SAR images by local averaging, while preserving the polarimetric information.

Parameters

Name	Type	Caption	Length	Value range
FILI*	String	Input polarimetric SAR image	1 - 192
FILO*	String	Output filtered polarimetric SAR image	1 - 192
FLSZ	Integer	Filter size (pixels, lines)	0 - 2	1 | 3 | 5 | 7 | 9 | 11 | 13 | 15 | 17 | 19 | 21 | 23 | 25 | 27 | 29 | 31 | 33 Default: 5,5
MONITOR	String	Monitor mode	0 - 3	ON, OFF Default: ON

* Required parameter

Parameter descriptions

FILI

The file name of the input polarimetric SAR image to filter.

The input data set must have already been imported into the PCIDSK (.pix) format with SARINGEST. Input can also be the key-file name of any GDB-supported POLSAR data set in its distribution format. For more information, including a complete list of supported SAR sensors and data products, follow the link to SARINGEST at the end of this topic.

FILO

The file name of the output filtered image. The number of output channels is the same as in the input image for detected data or when the input image is in covariance, coherency, or Kennaugh matrix format. However, when input data sets are in the scattering-matrix format, they are converted to the covariance-matrix format. For such data, the number of output channels depends on the symmetry of the input matrix and the number of polarizations.

The file name you specify must not already exist.

FLSZ

The filter size in the horizontal and vertical directions, in pixel units. The value you specify must be an odd integer between 1 and 33. The default value is 5,5 (5 x 5 pixels).

This parameter is optional.

MONITOR

The program progress can be monitored by printing the percentage of processing completed. A system parameter, MONITOR, controls this activity.

Available options are:

• ON: Turns the monitor ON (default)
• OFF: Turns the monitor OFF (recommended if running in batch or background mode)

Details

PSBOXCAR applies a boxcar filter to an input SAR data set. The boxcar filter replaces every image pixel by an average of pixel values in a window centered on the pixel. All of the raster channels in the input image are filtered independently.

Boxcar filtering is usually used to increase the estimated number of looks (ENL) in the data. This is required if an algorithm requires a minimum ENL that is higher than the ENL of the input data.

The input image must be a data set already imported into the PCIDSK (.pix) format by SARINGEST. Input can also be the key file name of any GDB-supported POLSAR data set in its distribution format. For more information, including a complete list of supported SAR sensors and data products, follow the link to SARINGEST at the end of this topic.

For input data in all other matrix formats, the output matrix type and the number of channels in the output are the same as those in the input. PSBOXCAR also accepts detected data. The data is boxcar averaged, and the number of output channels is equal to the number of input channels. The physical quantity of output pixel values (sigma0, beta0, or gamma0) is always the same as in the input data set.

Example

Filter a RADARSAT-2 data set to increase its ENL to 25. The data set has already been imported into the PCIDSK (.pix) format by SARINGEST.

        EASI>FILI="rsat2.pix" 
        EASI>FILO="rsat2_psboxcar5by5.pix"
        EASI>FLSZ=5,5

        EASI>run PSBOXCAR
      

Acknowledgements

PCI Geomatics gratefully acknowledges the financial support provided by the Canadian Space Agency through the Earth Observation Application Development Program (EOADP), contract number 9F028-034946.