- Basic patch based indices
r.pi.index [-a] input=name output=name keyval=integer method=string [title="phrase"] [--overwrite] [--help] [--verbose] [--quiet] [--ui]
- Set for 8 cell-neighbors. 4 cell-neighbors are default
- Allow output files to overwrite existing files
- Print usage summary
- Verbose module output
- Quiet module output
- Force launching GUI dialog
- 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 for resultant raster map
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).
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
provide the same analysis concerning the first nearest neighbour (NN),
but are extended to the n-th NN. However due to code construction does
distance analysis to first ENN perform faster.
operators determine what algorithm is applied
on the patches.
can perform the following operations:
- The Area computes the area of each patch.
- 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.
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:
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
Landscapes with more than 10 000 individual patches might cause a memory
allocation error depending on the user's system.
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
Available at: r.pi.index source code (history)
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GRASS Development Team,
GRASS GIS 7.8.5dev Reference Manual