GRASS GIS manual: r.li.patchdensity

NAME

r.li.patchdensity - Calculates patch density index on a raster map, using a 4 neighbour algorithm

KEYWORDS

raster, landscape structure analysis, patch index

SYNOPSIS

r.li.patchdensity
r.li.patchdensity help
r.li.patchdensity map=name conf=string output=name [--overwrite] [--verbose] [--quiet]

Flags:

--overwrite: Allow output files to overwrite existing files
--verbose: Verbose module output
--quiet: Quiet module output

Parameters:

map=name: Name of input raster map
conf=string: Configuration file
output=name: Name for output raster map

DESCRIPTION

r.li.patchdensity is a patch index for r.li suite. It calculates the function:

f(sample_area) = (Patch_Number/Area) * 1000000

that is 1000000 by number of patch for area unit. This index is calculated using a 4 neighbour algorithm.

EXAMPLES

To calculate patch density index on map my_map, using my_conf configuration file (previously defined with r.li.setup) and saving results in the raster map my_out, run:

r.li.patchdensity map=my_map conf=my_conf out=my_out

Example for Spearfish forest areas:

g.region rast=landcover.30m -p
# extract forested areas:
r.category landcover.30m
r.mapcalc "forests=if(landcover.30m >= 41 && landcover.30m <=43,1,null())"

# patch density (7x7 moving window defined in r.li.setup):
r.li.patchdensity forests conf=movwindow7 out=forests_p_dens7
d.rast.leg forests_p_dens7

r.to.vect forests out=forests feature=area
d.vect forests type=boundary

NOTES

A map of NULL values is considered to have zero patches.
If you want to have null values instead run

r.null setnull=0 map=my_out

after index calculation.
If raster area is 0, r.li.patchdensity returns -1. This is only possible if the raster is masked.

AUTHORS

Claudio Porta and Lucio Davide Spano, students of Computer Science University of Pisa (Italy).
Commission from Faunalia Pontedera (PI) (www.faunalia.it)

BUGS

Please send bugs reports to spano@cli.di.unipi.it, porta@cli.di.unipi.it

Last changed: $Date: 2008-02-19 12:12:24 -0800 (Tue, 19 Feb 2008) $