GRASS GIS manual: r.param.scale

Note: This document is for an older version of GRASS GIS that is outdated. You should upgrade, and read the current manual page.

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

SYNOPSIS

r.param.scale
r.param.scale help
r.param.scale [-c] input=name output=name [s_tol=float] [c_tol=float] [size=integer] [param=string] [exp=float] [zscale=float] [--overwrite] [--verbose] [--quiet]

Flags:

-c: Constrain model through central window cell
--overwrite: Allow output files to overwrite existing files
--verbose: Verbose module output
--quiet: Quiet module output

Parameters:

input=name: Name of input raster map
output=name: Output raster layer containing morphometric parameter
s_tol=float: Slope tolerance that defines a 'flat' surface (degrees); Default: 1.0
c_tol=float: Curvature tolerance that defines 'planar' surface; Default: 0.0001
size=integer: Size of processing window (odd number only, max: 69); Default: 3
param=string: Morphometric parameter in 'size' window to calculate; Options: elev,slope,aspect,profc,planc,longc,crosc,minic,maxic,feature; Default: elev
exp=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 DEM. 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 or 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 or plan curvature (horizontal curvature, intersecting with the XY plane)
longc or longitudinal curvature (profile curvature intersecting with the plane defined by the surface normal and maximum gradient direction)
crosc or 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 or maximum curvature (can be in any direction)
minic or 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.

Still to do

Fix bug when `constrain through central cell' option selected. Create color tables for all output files (presently only on features).

EXAMPLE

The next commands will create a geomorphological map of the Spearfish region:

g.region rast=elevation.10m -p
r.param.scale in=elevation.10m output=morphology param=feature size=9
d.mon x0
d.rast.leg morphology

r.param.scale generated geomorphological map

Geomorphological map of a subregion in the Spearfish (SD) area

REFERENCE

Wood, J. (1996): The Geomorphological characterisation of Digital Elevation Models. Diss., Department of Geography, University of Leicester, U.K.
online at:
http://www.soi.city.ac.uk/~jwo/phd/

AUTHOR

jwo@le.ac.uk - ASSIST's home

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

Last changed: $Date: 2009-04-02 23:15:59 -0800 (Thu, 02 Apr 2009) $

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