r.param.scalegrass - Online in the Cloud

PROGRAM:

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 region:
g.region raster=elevation.10m -p
r.param.scale in=elevation.10m output=morphology param=feature size=9

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://www.soi.city.ac.uk/~jwo/phd/

Java Code in LandSerf that implements the same procedure

Use r.param.scalegrass online using onworks.net services