NISAR Provisional Geocoded Polarimetric Covariance Product (Version 1)

The GCOV product provides terrain-corrected polarimetric covariance projected onto a predefined Universal Transverse Mercator (UTM) or polar stereographic projection system grid. RSLC radar samples, organized as a polarimetric scattering vector, are cross-correlated with the scattering vector’s conjugate transpose, originating the polarimetric covariance matrix expressed in the same grid as the RSLC range-Doppler grid.

The magnitude of the resulting polarimetric covariance terms is strongly affected by the topography, with areas facing the sensor becoming brighter and areas away from the sensor turning darker in the images, biasing covariance measurements. To reduce the effect of the topography, an area-based radiometric terrain correction (RTC) is applied over the covariance terms, normalizing the backscatter coefficient from beta-naught to gamma-naught.