Two morphological methods for edge detection in range images are proposed. The first method uses the opening and closing residues of structuring elements in orthogonal directions to detect roof and crease edges, and is essentially a morphological implementation of residue analysis techniques. The more general second method is based on a morphological version of the first derivative operator. This method utilizes dilation and erosion residues of structuring elements at different scales to reliably extract step edges along with roof edges and crease edges, and to classify each pixel as belonging to eight possible structure types: positive roof, negative roof, positive crease, negative crease, top of step, base of step, ramp, and constant surface. This method may be thought of as a morphological multiscale method.>