## DESCRIPTION

r.param.scale extracts terrain parameters from a digital elevation model. Uses a multi-scale approach by fitting a bivariate quadratic polynomial to a given window size using least squares.

The module calculates the following parameters (terminology is from Wood, 1996 with related terminology used in other GRASS modules listed in brackets):

- elev: Generalised elevation value (for resampling purposes at different scale)
- slope: Magnitude of maximum gradient (steepest slope angle)
- aspect: Direction of maximum gradient (steepest slope direction=flow direction)
- profc: profile curvature (curvature intersecting with the plane defined by Z axis and maximum gradient direction). Positive values describe convex profile curvature, negative values concave profile curvature.
- planc: plan curvature (horizontal curvature, intersecting with the XY plane)
- longc: longitudinal curvature (profile curvature intersecting with the plane defined by the surface normal and maximum gradient direction)
- crosc: cross-sectional curvature (tangential curvature intersecting with the plane defined by the surface normal and a tangent to the contour - perpendicular to maximum gradient direction)
- maxic: maximum curvature (can be in any direction)
- minic: minimum curvature (in direction perpendicular to the direction of of maximum curvature)
- feature: Morphometric features: peaks, ridges, passes, channels, pits and planes

## NOTES

In r.param.scale the direction of maximum gradient (considered downslope) is stored as (West is 0 degree, East is +/- 180 degree):

- 0..+180 degree from West to North to East
- 0..-180 degree from West to South to East

Note that the aspect map is calculated differently from r.slope.aspect.

## EXAMPLE

The next commands will create a geomorphological map of the Spearfish sample dataset region:

    g.region raster=elevation.10m -p
    r.param.scale in=elevation.10m output=morphology method=feature size=9

Figure: Geomorphological map of a subregion in the Spearfish (SD) area

## TODO

Fix bug when `constrain through central cell' option selected. Create color tables for all output files (presently only on features).

## REFERENCES

- Wood, J. (1996): The Geomorphological characterisation of Digital Elevation Models. Diss., Department of Geography, University of Leicester, U.K
  online at: http://hdl.handle.net/2381/34503
- Java Code in LandSerf that implements the same procedure

## SEE ALSO

r.geomorphon, r.slope.aspect

## AUTHORS

Update to FP 3/2002: L. Potrich, M. Neteler, S. Menegon (ITC-irst)

Last changed: $Date: 2017-11-03 17:43:02 +0100 (Fri, 03 Nov 2017) $