SARPolarSynth¶

Detailed description¶

This application gives, for each pixel, the power that would have been received by a SAR system with a basis different from the classical (H,V) one (polarimetric synthetis). The new basis A and B are indicated through two Jones vectors, defined by the user thanks to orientation (psi) and ellipticity (khi) parameters. These parameters are namely psii, khii, psir and khir. The suffixes (i) and (r) refer to the transmiting antenna and the receiving antenna respectively. Orientations and ellipticities are given in degrees, and are between -90/90 degrees and -45/45 degrees respectively.

Four polarization architectures can be processed : 1) HH_HV_VH_VV : full polarization, general bistatic case. 2) HH_HV_VV or HH_VH_VV : full polarization, monostatic case (transmitter and receiver are co-located). 3) HH_HV : dual polarization. 4) VH_VV : dual polarization. The application takes a complex vector image as input, where each band correspond to a particular emission/reception polarization scheme. User must comply with the band order given above, since the bands are used to build the Sinclair matrix.

In order to determine the architecture, the application first relies on the number of bands of the input image. 1) Architecture HH_HV_VH_VV is the only one with four bands, there is no possible confusion. 2) Concerning HH_HV_VV and HH_VH_VV architectures, both correspond to a three channels image. But they are processed in the same way, as the Sinclair matrix is symmetric in the monostatic case. 3) Finally, the two last architectures (dual polarizations), can’t be distinguished only by the number of bands of the input image.

User must then use the parameters emissionh and emissionv to indicate the architecture of the system : emissionh=1 and emissionv=0 –> HH_HV, emissionh=0 and emissionv=1 –> VH_VV.

Note : if the architecture is HH_HV, khii and psii are automatically both set to 0 degree; if the architecture is VH_VV, khii and psii are automatically set to 0 degree and 90 degrees respectively.

It is also possible to force the calculation to co-polar or cross-polar modes. In the co-polar case, values for psir and khir will be ignored and forced to psii and khii; same as the cross-polar mode, where khir and psir will be forced to (psii + 90 degrees) and -khii.

Finally, the result of the polarimetric synthetis is expressed in the power domain, through a one-band scalar image. Note: this application doesn’t take into account the terms which do not depend on the polarization of the antennas. The parameter gain can be used for this purpose.

More details can be found in the OTB CookBook (SAR processing chapter).

Parameters¶

This section describes in details the parameters available for this application. Table [1] presents a summary of these parameters and the parameters keys to be used in command-line and programming languages. Application key is SARPolarSynth .

• Input Image: Input image.
• Output Image: Output image.
• psii: Orientation (transmitting antenna).
• khii: Ellipticity (transmitting antenna).
• psir: Orientation (receiving antenna).
• khir: Ellipticity (receiving antenna).
• Emission H: This parameter is useful in determining the polarization architecture (dual polarization case).
• Emission V: This parameter is useful in determining the polarization architecture (dual polarization case).
• Forced mode: Available choices are:
• None : Copolarization
• Copolarization
• Crosspolarization : Crosspolarization
• Available RAM (Mb): Available memory for processing (in MB).
• Load otb application from xml file: Load otb application from xml file.
• Save otb application to xml file: Save otb application to xml file.

Example¶

To run this example in command-line, use the following:

otbcli_SARPolarSynth -in sar.tif -psii 15. -khii 5. -psir -25. -khir 10. -out newbasis.tif

To run this example from Python, use the following code snippet:

#!/usr/bin/python

# Import the otb applications package
import otbApplication

# The following line creates an instance of the SARPolarSynth application
SARPolarSynth = otbApplication.Registry.CreateApplication("SARPolarSynth")

# The following lines set all the application parameters:
SARPolarSynth.SetParameterString("in", "sar.tif")

SARPolarSynth.SetParameterFloat("psii", 15.)

SARPolarSynth.SetParameterFloat("khii", 5.)

SARPolarSynth.SetParameterFloat("psir", -25.)

SARPolarSynth.SetParameterFloat("khir", 10.)

SARPolarSynth.SetParameterString("out", "newbasis.tif")

# The following line execute the application
SARPolarSynth.ExecuteAndWriteOutput()