r.param.scale

NAME

r.param.scale - GRASS module that 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.

Usage:

r.param.scale [-c] in=name out=name [s_tol=value] [c_tol=value] [size=value] [param=name] [exp=value] [zscale=value]

Flags:

-c Constrain model through central window cell

Parameters:

in Input elevation raster

out Output raster representing the selected morphometric parameter

s_tol Slope tolerance that defines a `flat' surface (degrees)
default: 1.0

c_tol Curvature tolerance that defines `planar' surface
default: 0.0001

size Size of processing window (odd numbers only)
default: 3

param Morphometric parameter to calculate
options: elev,slope,aspect,profc,planc,longc,crosc,minic,maxic, feature
default: elev

exp Exponent for distance weighting (0.0-4.0)
default: 0.0

zscale Vertical scaling factor
default: 1.0

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)
meanc or mean curvature (average of maximum and minimum curvatures).
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).

REFERENCE

Wood, J. (1996): The Geomorphological characterisation of Digital Elevation Models. Diss., Department of Geography, University of Leicester, U.K.
online at:
www.geog.le.ac.uk/jwo/research/dem_char/thesis/index.html

AUTHOR

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

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

Last changed: $Date$