Optical Polarization - Remote Sensing Center
Optical Polarization
Polarimetry
Light, a form of electromagnetic radiation, has as one of its fundamental characteristics an intrinsic polarization. The polarization of the light refers to the direction of wave vibration in relation to the direction of propagation. The degree of polarization in reflected light is affected by a variety of factors including the illumination, surface roughness, color, and sensing geometry.
The Polarization Imaging camera measures the amount of polarized light at -45°, 0°, 45°, and 90° nearly simultaneously. These measurements are used to calculate Stokes vectors for each pixel in the image. Stokes S0 vector is the total intensity, S1 is the difference in vertical and horizontal polarization, and S2 is the difference in 45° and -45° polarization.
Degree of Linear Polarization (DOLP) is calculated according to the following relationship:
IED Detection
Research performed in 2009 tested the ability of the Bossa Nova Technology SALSA polarimetric camera to detect disturbed dirt and asphalt. Improvised Explosive Devices (IEDs) are often buried, which leaves them covered with disturbed dirt. The polarization signature of disturbed dirt was not strong compared to undisturbed dirt, but the camera was better able to distinguish between the polarization characteristics of patched or disturbed asphalt and the surrounding pavement, particularly when maximum likelihood classification was applied.
Disturbed asphalt with varying dirt coverage