---
name: "r.param.scale"
section: "1grass"
platform: "linux"
package: "grass-doc"
version: "8.4.1-1"
release: "Debian 13 (Trixie)"
platforms: ["linux"]
url: "https://new.carta.tech/r.param.scale"
---

# r.param.scale(1grass)

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

## 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)

Accessed: Monday Feb 24 17:50:45 2025

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