Integration of Landsat and SAR images based on intensity modulation

The paper presents a multisensor image fusion algorithm which extends the solutions proposed for pan-sharpening of multispectral (MS) data through intensity modulation, to the integration of SAR and multispectral imagery. The algorithm is based on the computation of the ratio between a speckle-filtered SAR image and a low-pass approximation, obtained by 'à-trous' wavelet decomposition, of the same filtered SAR image. This ratio modulates the intensity of the multispectral image, which is obtained by applying a linear transformation, i.e., a generalized IHS transform, to the original MS data. The modulated intensity image substitutes the original intensity image of the multispectral data and the inverse transform is applied to obtain the fused multispectral image. Experimental results are presented on Landsat ETM+ and ERS SAR images of an urban area. The results prove accurate spectral preservation on vegetated regions, bare soil, and also on textured areas (buildings and road network) where information from SAR enhances the fused result which can be successfully applied both for display and classification purposes.