Orthoimages are produced from conventional aerial photographs and are subject to all of the vagrancies of the photographic process. Though care is taken to use images taken when the sun angle is high, shadows still occur. This is particularly so in images of alpine terrain due to the steep slopes that are often present. To determine surface type at each location in an orthoimage, it is desirable to first reduce those brightness effects in the image that are due to shading rather than surface reflectivity. In order to render a view with a simulated sun angle different from the actual sun angle when the image was required, this same shading normalization must be accompanied by a process that removes the existing shadows.