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NAME

r.convergence

KEYWORDS

SYNOPSIS

r.convergence
r.convergence help
r.convergence [-cs] input=name output=name window=integer weights=string [--overwrite] [--verbose] [--quiet]

Flags:

-c
Use circular window (default: square)
-s
Add slope convergence (radically slow down calculation time)
--overwrite
Allow output files to overwrite existing files
--verbose
Verbose module output
--quiet
Quiet module output

Parameters:

input=name
Digital elevation model map
output=name
Output convergence index map
window=integer
Window size
Default: 3
weights=string
Method for reducing the impact of the cell due to distance
Options: standard,inverse,power,square,gentle
Default: standard

DESCRIPTION

How convergence index is calculated (3 x 3 window):

Convergence index is a terrain parameter which show the structure of the relief as a set of convergent areas (channels) and divergent areas (ridges). It represents the agreement of aspect direction of surrounding cells with the teoretical matrix direction. Convergence index is mean (or weighted mean if weights are used) aspect difference between real aspect and theoretical maximum divergent direction matrix representing ideal peak (see figure) minus 90 degres. So if there is maximum agreement with divergent matrix the convergence index is (0 - 90) * 10/9 = -100. If there is ideal sink (maximum convergence) the convergence index is (180 -90) * 10/9 = 100. Slope and aspect ere calculated internaly with the same formula as in r.slope.aspect. Convergence index is very useful for analysis of lineaments especially represented by rigdes or chanell systems as well as valley recognition tool.

SEE ALSO

r.slope.aspect, r.param.scale, r.neighbour,

REFERENCES

Claps, P., Fiorentino, M., Oliveto, G., (1994), Informational entropy of fractal river networks, Journal of Hydrology, 187(1-2), 145-156 .

Bauer J., Rohdenburg H., Bork H.-R., (1985), Ein Digitales Reliefmodell als Voraussetzung fuer ein deterministisches Modell der Wasser- und Stoff-Fluesse, IN: Bork, H.-R., Rohdenburg, H., Landschaftsgenese und Landschaftsoekologie, Parameteraufbereitung fuer deterministische Gebiets-Wassermodelle, Grundlagenarbeiten zu Analyse von Agrar-Oekosystemen, 1-15.

Böhner J., Blaschke T., Montanarella, L. (eds.) (2008). SAGA Seconds Out. Hamburger Beiträge zur Physischen Geographie und Landschaftsökologie, 19:113

AUTHOR

Jarek Jasiewicz

Last changed: $Date: 2013-03-27 02:03:58 -0700 (Wed, 27 Mar 2013) $


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