On the Use of the Expanded Image in Quality Assessment of Pansharpened Images

This letter discusses whether the expanded multispectral image, i.e., the original multispectral image upsampled to the panchromatic scale, can be used during the assessment of the quality of pansharpened multispectral images. By considering Wald's protocol, the authors demonstrate that the adoption of the expanded image as the reference is erroneous and brings a quality assessment of the fused images that is misleading. In addition, some recommendations about the valid role of the expanded image are provided. The discussion is supported by a quantitative analysis and visual comparisons.