Effects of Aliasing and Mis-Registration on Pan-Sharpening Methods Based on Either Component Substitution or Multi- Resolution Analysis

In this paper, the characteristics of multi-spectral (MS) and panchromatic (P) image fusion, or pan-sharpening, methods, will be investigated. Depending on the way spatial details are extracted from P, such methods can be broadly labelled into two main classes, roughly corresponding to component substitution (CS), also known as projection substitution, and methods based on multi-resolution analysis (MRA), i.e. on digital filtering. Experimental results carried out on QuickBird and Ikonos data sets evidence that CS-based fusion is far less sensitive than MRAbased fusion to: a) registration errors, i.e. spatial misalignments between MS and P images, possibly originated by cartographic projection and resampling of individual data sets; b) aliasing occurring in MS bands and stemming from a modulation transfer function (MTF) of each MS channels that is excessively broad relatively to the spatial sampling interval. Simulated misalignments, carried out at full scale by means of a suitable quality evaluation protocol, have evidenced the qualityshift trade-off of the two classes: MRA methods yield a slightly superior quality in the absence of misalignments, but are more penalized, whenever shifts between MS and P are present, than CS methods, which produce a slightly lower quality in the ideal case, but are intrinsically more shift tolerant.