2.4.6 Specific SAR functionnalities

This section give access to specific treatments related to the SAR (Synthetic Aperture Radar) functionnalities.

Despeckle

SAR images are generally corrupted by speckle noise. To suppress speckle and improve the radar image interpretability lots of filtering techniques have been proposed. The module implements to well-known despeckle methods: Frost and Lee.

Compute intensity and log-intensity

Compute the derived intensity and log-intensity from the input SAR imagery.

Polarimetry

In conventional imaging radar the measurement is a scalar which is proportional to the received backscattered power at a particular combination of linear polarization (HH, HV, VH or VV). Polarimetry is the measurement and interpretation of the polarization of this measurement which allows to measure various optical properties of a material. In polarimetry the basic measurement is a 2x2 complex scattering matrix yielding an eight dimensional measurement space (Sinclair matrix). For reciprocal targets where HV = VH, this space is compressed to five dimensions: three amplitudes (|HH|, |HV|, and |VV|); and two phase measurements, (co-pol: HH-VV, and cross-pol: HH-HV). (see grss-ieee).

Synthesis Allow to construct an image that would be received from a polarimetric radar having selected transmit and receive polarizations. The Synthesis module waits for real and imaginary part (real images) of the HH, VV, VH and HV images. The reciprocal case where case VH = HV , is not properly handled yet, for now the user has to set the same input for the two HV and VH.

Conversion As we saw in the previous main section, the basic measurement is a 2x2 complex scattering matrix yielding an eight dimensional measurement space. But other measurements exist:

Modules in the Conversion subsection allow to proceed these conversions between matrix representations. Allowed conversion and input images types are described in the following figure  2.18.


PIC

Figure 2.18: SAR polarimetry conversion module.


Analysis This module allows to perform some of classical polarimetric analysis methods. It allows to compute: