PSCC

Description

PSCC derives a correlation coefficient between two polarizations of a multilook dual-polarimetric, compact-polarimetric, or full-quad polarimetric SAR data set. The module also supports the ability to determine the correlation coefficients for synthesized polarizations provided the input file is a full-quad data set. With compact-pol or dual-pol data sets, you must specify one of the available polarizations.

Parameters

Name	Type	Caption	Length	Value range
FILI*	String	Input polarimetric SAR image	1 - 192
FILO*	String	Output correlation coefficient raster	1 - 192
POL1	String	First input polarization	0 - 192	Default: HH
POL2	String	Second input polarization	0 - 192	Default: VV
ANGLETYP	String	Angle units	0 - 7	Degrees | Radians Default: Degrees
MONITOR	String	Monitor mode	0 - 3	ON, OFF Default: ON

* Required parameter

Parameter descriptions

FILI

The name of the input SAR image, which could be detected, or complex data in any supported matrix format (covariance, coherence, or Kennaugh). The input data set should have an equivalent number of looks (ENL) of at least 25, which could be achieved by applying a polarimetric filter, such as boxcar, when the input data set is single-look complex.

The input data set must already have been imported into the PCIDSK format with SARINGEST. For more information, including a complete list of supported polarimetric SAR sensors and data products, follow the link to SARINGEST at the end of this topic.

FILO

The name of the output file to which to write the correlation coefficient. The output file has the same dimensions as the input SAR image. With complex input data, the output file has four floating-point channels that contain the magnitude, phase, real, and imaginary parts of the complex correlation coefficient at every pixel. The phase of the correlation coefficient is equal to the phase difference between the selected polarizations. With detected input data, the output file has only one channel that contains the magnitude of the scalar correlation coefficient at every pixel.

The file name you specify must not already exist.

POL1

The first polarization in the input file to use. The default value is HH.

With full-quad data sets, you can, as an option, synthesize any polarization of interest. For more information, follow the link to PSPOLSYN at the end of this topic, and see the Details section.

Standard configurations, such as linear-horizontal (H), linear-vertical (V), left-circular (L), and right-circular (R) are supported. Non-standard configurations require four floating-point values; orientation and ellipticity for transmit, followed by orientation and ellipticity for receive. Valid orientation angles range from -90 to 90. Valid ellipticity angles range from -45 to 45.

• rh: case-insensitive, predefined transmit and receive
• Rh: case-insensitive, predefined transmit and receive
• rH: case-insensitive, predefined transmit and receive
• 0,-45,H: transmit TPSI and TCHI followed by predefined receive
• 0,-45,h: transmit TPSI and TCHI followed by predefined receive
• R,0,0: predefined transmit followed by receive RPSI and RCHI
• r,0,0: predefined transmit followed by receive RPSI and RCHI
• 0,-45,0,0: transmit TPSI and TCHI followed by receive RPSI and RCHI

This parameter is optional.

POL2

The second polarization in the input file to use. The default value is VV. The behavior of this parameter is identical to that of POL1.

This parameter is optional.

ANGLETYP

The angle units for the output correlation coefficient phase channel, in degrees or radians. This parameter is ignored when the input SAR image is not complex. The default is Degrees.

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

PSCC computes the correlation coefficient between two polarizations of a polarimetric SAR image at every pixel. With complex input data, a complex correlation coefficient is derived. With detected input data, a scalar correlation coefficient is computed at every pixel.

With full-quad input, you can, as an option, select synthesized polarizations to use as input for the calculation of the correlation coefficients.

With detected input data sets, a correlation coefficient value of 0.0 indicates an invalid result. If any of the magnitudes involved is zero, the correlation coefficient cannot be computed.

You can calculate the correlation coefficient for dual-polarized ENVISAT ASAR alternating polarization mode, but since they have no Doppler overlap, the two channels are incoherent (relative to each other) and therefore, the correlation coefficient is not expected to provide any useful information.

Similarly, RADARSAT-2 dual-polarized data provides combinations of co-polarization and cross-polarization (HH+HV or VV+VH). Over most targets, the correlation coefficient between co-polarized and cross-polarized channels is low and provides little information, but can be useful in assessing the calibration and image quality. The correlation coefficient between co-polarized channels (HH+VV) is of much greater interest. Therefore, typically only co-polarized channels are used for the first and second input polarizations.

Examples

Derive the complex correlation coefficient for the two co-polarizations of a RADARSAT-2 data set that is already imported into the PCIDSK format. Specify the phase angle in degrees.

        EASI>FILI="rsat2_slc.pix" 
        EASI>FILO="rsat2_pscc_HH_VV.pix" 
        EASI>POL1="HH" 
        EASI>POL2="VV" 
        EASI>ANGLETYP="" 
        EASI>run PSCC 
      

Derive the complex correlation coefficient for synthesized polarizations RR and LL from a full-quad multilook RADARSAT-2 data set that is already imported into the PCIDSK format. Specify the phase angle in degrees

        EASI>FILI="rsat2_full_quad_filtered.pix" 
        EASI>FILO="rsat2_pscc_RR_LL.pix" 
        EASI>POL1="RR" 
        EASI>POL2="LL" 
        EASI>ANGLETYP="" 
        EASI>run PSCC 
      

Derive the complex correlation coefficient for synthesized polarizations for RH and RV using the transmit and receive orientation and ellipticity values from a full-quad multilook RADARSAT-2 data set that is already imported into the PCIDSK format. Specify the phase angle in radians.

        EASI>FILI="rsat2_full_quad_filtered.pix" 
        EASI>FILO="rsat2_pscc_RH_RV.pix" 
        EASI>POL1="0 -45, 0, 0" 
        EASI>POL2="0, -45, 90, 0" 
        EASI>ANGLETYP="Radians" 
        EASI>run PSCC 
      

Derive the complex correlation coefficient for HH and HV data from a multilook, dual-pol, Sentinel-1 data set. Specify the phase angle in radians.

        EASI>FILI="sentinel_1_dual_pol_filtered.pix" 
        EASI>FILO="sentinel_1_pscc_HH_HV.pix" 
        EASI>POL1="hh" 
        EASI>POL2="hv" 
        EASI>ANGLETYP="Radians" 
        EASI>run PSCC
      

Algorithm

If required, the selected polarizations are synthesized. The complex-valued correlation coefficient (rho) is calculated as rho = (P1*conj(P2))/sqrt(P1^2*P2^2), where P1 and P2 are the complex-valued polarizations under consideration and conj is the complex conjugate.

The phase of the correlation is computed as ATAN2(Imag(rho), Real(rho)). Depending on the value specified for the ANGLETYP parameter, it returns the results between -180 and 180 degrees, or between -pi and pi radians.

The correlation magnitude, phase, real part, and imaginary part are written respectively to channels one to four.

When the input data set contains intensity or amplitude values, only the magnitude of the correlation coefficient is computed.

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.