A comparative assessment of different methods for Landsat 7/ETM+  pansharpening

Abstract

This article compares a set of relevant methods, based on different mathematical approaches, for Landsat 7 Enhanced Thematic Mapper Plus (ETM+) pansharpening. These are classical procedures such as principal component analysis and fast intensity hue saturation; methods based on wavelet transforms, such as wavelet à trous, additive wavelet luminance proportional and multidirectional–multiresolution methods; a method of a geostatistical nature, called downscaling cokriging (DCK); and finally, a Bayesian method (1cor). The comparison of the fused images is based on the qualitative and quantitative evaluation of their spatial and spectral characteristics by calculating statistical indices and parameters that measure the quality and coherence of the images. Moreover, the quality of the spectral information is studied indirectly by means of the Iterative Self-Organizing Data Analysis Technique (ISODATA) classification of the products of fusion. The results show that DCK and 1cor methods yielded better results than the wavelet-based methods. Particularly, DCK does not introduce artefacts in the estimation of the digital numbers corresponding with the source multispectral image and, therefore, it can be considered as the most coherent method.

Acknowledgements

The authors are grateful to the Spanish MICINN (CGL2010–17629 and CGL2010–15498) and Junta de Andalucía (Group RNM122) for the financial support. This work has also been partially supported by the Comisión Nacional de Ciencia y Tecnología, under contract TIN2010–15137, and the Consejería de Innovación, Ciencia y Empresa of the Junta de Andalucía, under contract P07–TIC–02698. The wavelet methods WAT and MDMR have been applied using the framework IJFUSION, which has been developed by the Remote Sensing Group at the Faculty of Computer Science, Universidad Politécnica de Madrid.