Relief shading can be a very effective way of presenting spatial datasets. By treating the data as if it is a 3D surface and generating shading corresponding to the surface being ‘illuminated’ from some direction, we can use the eye's innate ability to interpret shading patterns to invoke a perception of 3D morphology. However, while interpretation of the form of data is enhanced, any sense of the actual data values is diminished because shading only depends on the surface gradient. This can be remedied to some degree by using colour to convey the value information that is lost in relief shading. Another reason for using colour in conjunction with relief shading is that can enhance the perception of shape induced by the shading. However, if colour is mis-used it is also potentially destructive of the visualisation benefits of relief shading.