First steps towards multimodal georeferencing of 3D VHR optical and X-band SAR imagery

With the advent of new, more widely available very high resolution (VHR) SAR and optical sensor satellite constellations, the issue of jointly exploiting the corresponding imaging data in the best possible way naturally arises. Our ultimate goal is the pixel-level fusion of these modalities and their visualization in a 3D context, i.e. draped over terrain data, itself obtained from interferometric SAR processing. In this paper, we investigate the issues associated with adapting tools originally developed for low-resolution C-band SAR imagery to high-resolution X-band SAR imagery (both spaceborne). Specifically, we consider the issues associated with SAR interferometry (InSAR) and more particularly those associated with complex interpolation and phase unwrapping. We found that the existing chirp-Z transform complex interpolator previously used at low resolution is perfectly suitable for handling VHR SAR data. We also found that, while the selected phase unwrapping procedure works well when the resolution is reduced by averaging, it is deficient at full resolution, in part due micro-reliefs and specific phase responses.