elev:     Generalised elevation value.
     slope:    Maximum gradient at a point.
     aspect:   Direction of maximum gradient.
     profc:    Profile convexity (vertical in direction of steepest slope).
     planc:    Plan convexity (contour curvature).
     crosc:    Cross sectional convexity (tangent to contours, downslope).
     longc:    Longitudinal convexity (perpendicular to contours downslope).
     minic:    Minimum convexity.
     maxic:    Maximum convexity.
     feature:  Morphometric features:
                 peaks, ridges, passes, channels, pits and planes.
     resid:
     moran: Moran statistics
     geary:
Last changed: $Date: 2002/01/25 05:45:33 $