Polarization

The polarization of electromagnetic (EM) waves indicates the orientation in which the wave’s electrical field moves with respect to its direction of motion. Linear polarized EM waves have the electrical field oriented either horizontally or vertically. In some cases, the polarization of a transmitted wave is modified by a scatterer, which then contains additional information on the scatterer. Therefore SAR (and other) radar systems have the capability to detect these polarization modifications. The Sentinel-1 C-SAR discerns four different polarization modes:

• HH - for horizontal transmit and horizontal receive
• VV - for vertical transmit and vertical receive
• HV - for horizontal transmit and vertical receive
• VH - for vertical transmit and horizontal receive

The first two polarization combinations are referred to as like-polarized, because the transmit and receive polarizations are similar.
The last two combinations are referred to as cross-polarized, because the transmit and receive polarizations directions are perpendicular.
A conceptual image of the like-polarization modes is shown in Figure 1.

Figure 1: Schematic presentation of VV and HH polarization.