Spectral information extraction by means of MS+PAN fusion

This paper deals with multi-spectral (MS) and panchromatic (Pan) image fusion based on redundant multiresolution analysis (MRA). Lower-resolution MS bands are sharpened by injecting high-pass details taken from the higher-resolution Pan image. Crucial point is modelling the relationships between detail coefficients of a generic MS band and the Pan image at the same resolution. Once calculated at the coarser resolution, where both types of data are available, such a model shall be extended to the finer resolution to weight the Pan details to be injected. Two injection models embedded in an "à trous" wavelet decomposition will be described and compared on a test set of very high resolution QuickBird MS+Pan data. One works on approximations and provides a partial unmixing of coarse MS pixels via high-resolution Pan. Another is based on spectral fidelity of the merged image to the original MS data. Fusion comparisons on spatially degraded data, of which higher-resolution true MS data are available for reference, show that the former yields better results than the latter, in terms of both spatial and spectral fidelity.