Need for developing repeat-pass differential POLSAR interferometry

Radar Polarimetry, Radar Interferometry and Polarimetric SAR Interferometry represent the current culmination in active ‘Microwave Remote Sensing’ technology, but we still need to progress very considerably in order to reach the limits of physical realizability. Whereas with radar polarimetry the textural fine-structure, target orientation, symmetries and material constituents can be recovered with considerable improvement above that of standard ‘amplitude-only’ radar; by implementing ‘radar interferometry’ the spatial (in depth) structure can be explored. With Polarimetric Interferometric Synthetic Aperture Radar (POL-IN-SAR) imaging, it is possible to recover such co-registered textural and spatial information from POL-IN-SAR digital image data sets simultaneously, including the extraction of Digital Elevation Maps (DEM) from either Polarimetric (scattering matrix) or Interferometric (dual antenna) SAR systems. Simultaneous Polarimetric-plus- Interferometric SAR Imaging offers the additional benefit of obtaining co-registered textural-plus-spatial three-dimensional POL-IN-DEM information, which when applied to Repeat-Pass Image-Overlay Interferometry provides differential background validation and environmental stress-change information with highly improved accuracy. However, hitherto only single-polarization-channel repeat-pass IN-SAR was developed and considered; and therefore the aim of this paper is to scrutinize and determine why and for what specific problems fully polarimetric differential RP-POL-IN-SAR imaging is required.