A critical review of fusion methods for true colour display of very high resolution images of urban areas

This paper critically reviews state-of-the-art and advanced methods for multi-spectral (MS) and panchromatic (Pan) image fusion based on either intensity-hue-saturation (IHS) transformation, or redundant multi-resolution analysis (MRA). In either cases, lower-resolution MS bands are sharpened by injecting 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 a generalised Laplacian pyramid (GLP) decomposition will be compared on a test set of very high resolution QuickBird MS+Pan data.