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r.param.scale(1grass) GRASS GIS User's Manual r.param.scale(1grass)


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


Name of input raster map

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 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


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


r.geomorphon, r.slope.aspect


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


Available at: r.param.scale source code (history)

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GRASS 7.8.5