r.pi.index - GRASS GIS manual

NAME

r.pi.index - Basic patch based indices

KEYWORDS

SYNOPSIS

r.pi.index

r.pi.index --help

r.pi.index [-a] input=name output=name keyval=integer method=string [title="phrase"] [--overwrite] [--help] [--verbose] [--quiet] [--ui]

Flags:

-a: Set for 8 cell-neighbors. 4 cell-neighbors are default
--overwrite: Allow output files to overwrite existing files
--help: Print usage summary
--verbose: Verbose module output
--quiet: Quiet module output
--ui: Force launching GUI dialog

Parameters:

input=name [required]: Raster map containing categories
output=name [required]: Output patch-based result as raster map
keyval=integer [required]: The value of the class to be analysed
method=string [required]: Operation to perform on fragments; Options: area, perimeter, shape, border, compactness, asymmetry, area-perimeter, fractal, ENN
title="phrase": Title for resultant raster map

DESCRIPTION
NOTES
EXAMPLE
SEE ALSO
BUGS
AUTHORS

DESCRIPTION

r.pi.index is a patch based fragmentation analysis package. Computation of basic fragmentation indices can be accomplished.

Available options for the index to be computed for patches within a certain class are: area (area), perimeter (perim), SHAPE (shape), Border-Index (bor), Compactness (comp), Asymmetry (asym), area-perimeter ratio (apr), fractal dimension (fract), distance to euclidean nearest neighbour (ENN).

NOTES

The Nearest Neighbour Index (ENN) analyse the Euclidean Nearest Neighbour to the first neighbouring patch. The output value is in pixel and can be converted to a distance values using g.region resolution information. r.pi.enn and r.pi.fnn provide the same analysis concerning the first nearest neighbour (NN), but are extended to the n-th NN. However due to code construction does the r.pi.index distance analysis to first ENN perform faster. Methods: The method operators determine what algorithm is applied on the patches. r.pi.index can perform the following operations:

Area: The Area computes the area of each patch.
Perimeter: The Perimeter computes the perimeter of each patch.
Area-Perimeter ratio: The Area-Perimeter ratio divides the patch perimeter by the area.
SHAPE Index: The SHAPE Index divides the patch perimete by the minimum perimeter possible for a maximally compact patch of the corresponding patch area.
Border Index: The Border Index ....
Compactness Index: The Compactness Index ....
Asymmetry Index: The Border Index ....
Fractal Dimension Index: The Fractal Dimension Index ....
Nearest Neighbour Index: The Nearest Neighbour Index computes the Euclidean distance to the first nearest neighbour patch.

EXAMPLE

Examples based on the North Carolina sample dataset are provided below. Indices are calculated for the landscape class 5 (forest). set region settings to used landcover class map:

g.region rast=landclass96

computation of patch size (patch definition: 4-neighbourhood rule)

r.pi.index input=landclass96 output=landclass96_forestclass5_area keyval=5 method=area
# improve colouring of resulting map: 
r.colors landclass96_forestclass5_area col=bgyr

computation of patch size (patch definition: 8-neighbourhood rule)

r.pi.index input=landclass96 output=landclass96_forestclass5_area keyval=5 method=area -a

computation of patch isolation (euclidean distance to 1. nearest neighbour; patch definition: 4-neighbourhood rule)

r.pi.index input=landclass96 output=landclass96_forestclass5_ENN keyval=5 method=ENN -a

BUGS

Landscapes with more than 10 000 individual patches might cause a memory allocation error depending on the user's system.

AUTHORS

Programming: Elshad Shirinov
Scientific concept: Dr. Martin Wegmann
Department of Remote Sensing
Remote Sensing and Biodiversity Unit
University of Wuerzburg, Germany

Port to GRASS GIS 7: Markus Metz

SOURCE CODE

Available at: r.pi.index source code (history)