## 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

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

## SOURCE CODE

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

Accessed: Tuesday Jun 16 04:04:44 2026

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