r.li.patchdensity1grass

Usage

Keywords

raster, landscape structure analysis, patch index

Overview

r.li.patchdensity calculates the "patch density index", the number of patches per square kilometer, as:

PD = Npatch / A

with:

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 config and output file/map parameters. 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 folder C:\Users\userxy\AppData\Roaming\GRASS8\r.li\output\ (MS-Windows) or $HOME/.grass8/r.li/output/ (GNU/Linux).

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 raster=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

Forest map (North Carolina sample dataset) example:

g.region raster=landclass96 -p
r.mapcalc "forests = if(landclass96 == 5, 1, null() )"
r.li.patchdensity input=forests conf=movwindow7 out=forests_patchdensity_mov7
# verify
r.univar forests_patchdensity_mov7
r.to.vect input=forests output=forests type=area
d.mon wx0
d.rast forests_patchdensity_mov7
d.vect forests type=boundary

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)

Source code

Available at: r.li.patchdensity source code (history)

Accessed: Monday Feb 24 17:50:45 2025

Main index | Raster index | Topics index | Keywords index | Graphical index | Full index

© 2003-2025 GRASS Development Team, GRASS GIS 8.4.1 Reference Manual