r.param.scale.1grass man page

r.param.scale — Extracts terrain parameters from a DEM.
Uses a multi-scale approach by taking fitting quadratic parameters to any size window (via least squares).


raster, geomorphology, terrain, elevation, landform


r.param.scale --help
r.param.scale [-c] input=name output=name  [slope_tolerance=float]   [curvature_tolerance=float]   [size=integer]   [method=string]   [exponent=float]   [zscale=float]   [--overwrite]  [--help]  [--verbose]  [--quiet]  [--ui]



Constrain model through central window cell


Allow output files to overwrite existing files


Print usage summary


Verbose module output


Quiet module output


Force launching GUI dialog


input=name [required]

Name of input raster map

output=name [required]

Name for output raster map containing morphometric parameter


Slope tolerance that defines a ’flat’ surface (degrees)
Default: 1.0


Curvature tolerance that defines ’planar’ surface
Default: 0.0001


Size of processing window (odd number only)
Options: 3-499
Default: 3


Morphometric parameter in ’size’ window to calculate
Options: elev, slope, aspect, profc, planc, longc, crosc, minic, maxic, feature
Default: elev


Exponent for distance weighting (0.0-4.0)
Default: 0.0


Vertical scaling factor
Default: 1.0


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


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.


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

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

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


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


Wood, J. (1996): The Geomorphological characterisation of Digital Elevation Models. Diss., Department of Geography, University of Leicester, U.K.
online at:

Java Code in LandSerf that implements the same procedure

See Also



jwo@le.ac.uk - ASSIST’s home

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

Last changed: $Date: 2015-07-20 10:49:51 +0200 (Mon, 20 Jul 2015) $

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