DESCRIPTION
r.li.patchdensity calculates the "patch density index",
the number of patches per square kilometer, as:
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 g.gui.rlisetup, then the
output will be a raster map, otherwise an ASCII file will be generated in
the $HOME/.grass7/r.li/output/ folder.
A sample area of only NULL values is considered to have zero patches,
that is, the result is always ≥ 0.
EXAMPLES
To calculate patch density index on map my_map, using
my_conf configuration file (previously defined with
g.gui.rlisetup) and saving results in my_out, run:
r.li.patchdensity input=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 g.gui.rlisetup):
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
g.gui.rlisetup
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
Michael Shapiro - CERL (patch identification)
Markus Metz (statistics)
Last changed: $Date$