r.param.scale(1)

📦
version 8.4.2 · 8 versions
, in fedora 44

💖 r.param.scale 💖

okay so bestie, welcome to the GRASS GIS User's Manual page for r.param.scale ✨ — this is the one that pulls terrain parameters out of a DEM, and it does it multi-scale style by fitting quadratic parameters to a window of literally any size (via least squares). no cap.

🌈 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. It uses a multi-scale approach by fitting a bivariate quadratic polynomial to a given window size using least squares. the way it just does that? iconic.

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 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
ngl bestie, note that the aspect map is calculated differently from r.slope.aspect. it's giving "same vibes, different math" 💀

🌸 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: Saturday Jan 17 05:40:54 2026

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© 2003-2025 GRASS Development Team, GRASS GIS 8.4.2 Reference Manual

and that's the whole page bestie, r.param.scale(1) from the GRASS GIS User's Manual, running on GRASS 8.4.2 — go make some beautiful terrain parameter maps, you absolute main character 🫶💖✨

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