Tool NameTopographic Position Index (TPI)
Tool ID18
Library IDta_morphometry
Version1.0
Author(s)O.Conrad (c) 2011

Please cite SAGA whenever you use it for your publications:

doi:10.5194/gmd-8-1991-2015

Description

Topographic Position Index (TPI) calculation as proposed by Guisan et al. (1999). This is literally the same as the difference to the mean calculation (residual analysis) proposed by Wilson & Gallant (2000). The bandwidth parameter for distance weighting is given as percentage of the (outer) radius.

Parameters

NameTypeIdentifierDescriptionConstraints
Input
Elevationgrid, inputDEM
Output
Topographic Position Indexgrid, outputTPI
Options
StandardizebooleanSTANDARDDefault: 0
Scalevalue rangeRADIUSkernel radius; defines an annulus if minimum is greater than zeroDefault: 0; 100
Radius UnitchoiceUNITAvailable Choices:
[0] map units
[1] cells
Default: 0
Weighting FunctionchoiceDW_WEIGHTINGAvailable Choices:
[0] no distance weighting
[1] inverse distance to a power
[2] exponential
[3] gaussian
Default: 0
Powerfloating point numberDW_IDW_POWERMinimum: 0.000000
Default: 2
Bandwidthfloating point numberDW_BANDWIDTHBandwidth for exponential and Gaussian weightingMinimum: 0.000000
Default: 75
Processing Buffer Distancefloating point numberPROC_BUFFERWidth of the buffer added around the central raster area [in radius unit]. Kernel cells within the buffered extent are evaluated, but TPI is calculated only for the inner (non-buffered) area. The buffer distance should match or exceed the maximum kernel radius to avoid edge effects.Minimum: 0.000000
Default: 0