Fusion of images and raster-maps of different spatial resolutions by encrustation: an improved approach

The present paper addresses the problem of the encrustation of a high spatial resolution imagette into an image of lower resolution of larger geographical extent. A method is proposed which makes use of the high resolution content of the imagette to simulate the high resolution content in the outer periphery of the imagette area. The originality of this approach lies into its ability to simultaneously attenuate the edges caused by the differences in resolution and increase the quality of the lower resolution image in the outer periphery in the sense that it becomes closer to the actual information at high resolution. These properties are demonstrated both visually and quantitatively. A SPOT image of the city of Barcelona (Spain) provides a didactic example of the problems and solutions as well as of the benefit of encrustation. The increase in quality compared with the standard raw encrustation procedure is quantitatively assessed for both the edge smoothing and the simulation of the actual information. Unsurprisingly the proposed approach provides better results than the standard method. It is illustrated by the construction of an albedo map for large Europe made up of three different images of different resolutions. Fusion of images and maps of different spatial resolutions. L. Wald, T. Ranchin 1