MULTIRESOLUTION IMAGE FUSION: PHASE CONGRUENCY FOR SPATIAL CONSISTENCY ASSESSMENT

Abstract

Multiresolution and multispectral image fusion (pan-sharpening) requires proper assessment of spectral consistency but also spatial consistency. Many fusion methods resulting in perfect spectral consistency may leak spatial consistency and vice versa, therefore a proper assessment of both spectral and spatial consistency is required. Up to now, only a few approaches were proposed for spatial consistency assessment using edge map comparison, calculated by gradient-like methods (Sobel or Laplace operators). Since image fusion may change intensity and contrast of the objects in the fused image, gradient methods may give disagreeing edge maps of the fused and reference (panchromatic) image. Unfortunately, this may lead to wrong conclusions on spatial consistency. In this paper we propose to use phase congruency for spatial consistency assessment. This measure is invariant to intensity and contrast change and allows to assess spatial consistency of fused image in multiscale way. Several assessment tests on IKONOS data allowed to compare known assessment measures and the measure based on phase congruency. It is shown that phase congruency measure has common trend with other widely used assessment measures and allows to obtain confident assessment of spatial consistency.