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=
name
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=name
-
Configuration file
- output=name
-
Name for output raster map
DESCRIPTION¶
r.li.patchdensity calculates the "patch density index", the
number of patches per square kilometer, as:
PD = Npatch / A
with:
- A:sampling area size
- Npatch: number of patches
This index is calculated using a 4 neighbour algorithm, diagonal cells are
ignored when tracing a patch.
NOTES¶
Do not use absolute path names for the
output map/file. If the
"moving window" method was selected in
r.li.setup, then the
output will be a raster map, otherwise an ASCII file will be generated in the
$HOME/.r.li/output/ folder.
A map of NULL values is considered to have zero patches.
If raster area is 0,
r.li.patchdensity returns -1. This is only possible
if the raster is masked.
If you want to change these -1 values to NULL, run subsequently on the resulting
map:
r.null setnull=-1 map=my_out
after index calculation.
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
my_out, run:
r.li.patchdensity map=my_map conf=my_conf output=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
r.univar forests_p_dens7
d.rast.leg forests_p_dens7
r.to.vect forests out=forests feature=area
d.vect forests type=boundary
SEE ALSO¶
r.li - package overview
r.li.setup
REFERENCES¶
McGarigal, K., and B. J. Marks. 1995. FRAGSTATS: spatial pattern analysis
program for quantifying landscape structure. USDA For. Serv. Gen. Tech. Rep.
PNW-351. (PDF)
AUTHORS¶
Claudio Porta and Lucio Davide Spano, students of Computer Science University of
Pisa (Italy).
Commission from Faunalia Pontedera (PI) (www.faunalia.it)
Last changed: $Date: 2014-02-19 01:26:04 +0100 (Wed, 19 Feb 2014) $
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