r.param.scale(1)

NAME
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).

KEYWORDS
raster, geomorphology, terrain, elevation, landform

SYNOPSIS
r.param.scale
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]

  Flags:

-c
    Constrain model through central window cell

--overwrite
    Allow output files to overwrite existing files

--help
    Print usage summary

--verbose
    Verbose module output

--quiet
    Quiet module output

--ui
    Force launching GUI dialog

  Parameters:

input=name [required]
    Name of input raster map

output=name [required]
    Name for output raster map containing morphometric parameter

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

curvature_tolerance=float
    Curvature tolerance that defines ’planar’ surface
    Default: 0.0001

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

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

exponent=float
    Exponent for distance weighting (0.0-4.0)
    Default: 0.0

zscale=float
    Vertical scaling factor
    Default: 1.0

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
Jo Wood - ASSIST’s home

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

SOURCE CODE

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

Latest change: Friday Apr 17 01:04:26 2026 in commit: 32a143358df26b2e518b03c7e0d79541e8d1e5b1

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