Twin Snakes for Determining Seam Lines in Orthoimage Mosaicking

As a last step in an orthophoto production process, called mosaicking, neighboring and partly overlapping images of a scene are merged to one image. This should be done in a way that the transition from one to the next image cannot be seen. The production line of orthophotos consists of several steps, each of which can introduce differences in overlapping orthophotos. For mosaicking these orthophotos, a seam line has to be delineated through the overlap area. In this paper, criteria for such an optimal seam line in color orthophotos are elaborated. The main requirements are maximum color similarity of the images (mainly in hue and intensity), and maximum texture similarity. Especially those areas are avoided, where many edges in radial direction can be found in one image, because these edges have another orientation in the neighboring image. The specified criteria are formulated in the energy function of snakes. Two snakes that attract one another (twin snakes) are initialized in a hierarchical strategy for detecting the seam line. The potential of the method is shown on an example.