Legend based elevation layers extraction from a color-coded relief scanned map

This paper presents an approach to extract the elevation layers from a color-coded relief scanned map having as an input information the colors provided by the map´s legend. We work in the CIE L*u*v* color space. The mean shift filtering is used to reduce the printing details (the dithering effect). The colors are extracted from the legend by the randomised local search (RES) algorithm. The elevation layers are identified by computing the Euclidean distance between each color in the legend and each pixel in the scanned image and then using a threshold operation. Overlaps between the extracted layers are also considered in order to eliminate distortions.