4.10.12 SARPolarSynth

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).

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° and -45°/45° 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 symetric 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 set to 0°/0°; if the architecture is VH_VV, khii and psii are automatically set to 0°/90°.

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° 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 4.176, page 851 presents a summary of these parameters and the parameters keys to be used in command-line and programming languages. Application key is SARPolarSynth.





Parameter key

Parameter type

Parameter description




in

Input image

Input Image

out

Output image

Output Image

psii

Float

psii

khii

Float

khii

psir

Float

psir

khir

Float

khir

emissionh

Int

Emission H

emissionv

Int

Emission V

mode

Choices

Forced mode

mode none

Choice

None

mode co

Choice

Copolarization

mode cross

Choice

Crosspolarization

ram

Int

Available RAM (Mb)

inxml

XML input parameters file

Load otb application from xml file

outxml

XML output parameters file

Save otb application to xml file











Table 4.176: Parameters table for SARPolarSynth.

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()

Limitations

None

Authors

This application has been written by OTB-Team.

See also

These additional ressources can be useful for further information: