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NAME

r.tpi - Calculates the multiscale topographic position index

KEYWORDS

raster

SYNOPSIS

r.tpi
r.tpi --help
r.tpi input=name minradius=integer maxradius=integer steps=integer output=name [--overwrite] [--help] [--verbose] [--quiet] [--ui]

Flags:

--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]
Elevation
Input DEM from which to calculate mTPI
minradius=integer [required]
Smoothing neighborhood radius size (minimum)
Minimum neighborhood radius in cells for DEM smoothing
Default: 1
maxradius=integer [required]
Smoothing neighborhood radius size (maximum)
Maximum neighborhood radius in cells for DEM smoothing
Default: 31
steps=integer [required]
Number of scaling steps
Number of steps to use for DEM generalization between minradius and maxradius
Default: 5
output=name [required]
Multi-scale topographic position index

Table of contents

DESCRIPTION

r.tpicalculates a multiscale version of the Topographic Position Index (TPI) of Guisan et al. (1999). The TPI is calculated by averaging a DEM over a user-specified moving window size and subtracting the original DEM from the averaged version to get the residual. This has the effect of extracting finer-scale landforms from regional-scale relief. Positive TPI values represent ridges or hills, and negative TPI values represent valleys or pits.

Unlike the original TPI, r.tpi implements a multiscale version that calculates a standardized TPI over multiple neighborhood radii from minradius to maxradius, starting at the largest neighborhood size. For subsequent steps, the standardized TPI is updated with pixels where the absolute TPI values exceed the TPI values of the previous step. For large neighborhoods > 15, resampling is used rather than a focal function to generalize the DEM.

EXAMPLE

g.region raster=elevation@PERMANENT -a
r.tpi input=elevation@PERMANENT minradius=1 maxradius=25 steps=5 output=tpi
Multiscale TPI

REFERENCES

Guisan, A., S. B. Weiss, A. D. Weiss 1999. GLM versus CCA spatial modeling of plant species distribution. Plant Ecology 143: 107-122

SEE ALSO

r.mapcalc,

AUTHOR

Steven Pawley

SOURCE CODE

Available at: r.tpi source code (history)


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