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

       jwo@le.ac.uk - 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)

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