SEM stereogrammetry with a low magnification mosaic of pictures is used to measure the elevation of many individual points. This random array of elevations is then connected into a triangular mesh, from which a contour map of elevation is drawn for the entire surface. Maps of surfaces before and after removal of material are used to determine the volume removed. The method is applicable to many circumstances of wear, erosion or deformation of surfaces. It is applied here to the erosion of human teeth due to dental polishing.