SAGA-GIS Tool Library Documentation (v7.8.2)

Tool Topographic Position Index (TPI)

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.


References


Parameters

 NameTypeIdentifierDescriptionConstraints
InputElevationGrid, inputDEM--
OutputTopographic Position IndexGrid, outputTPI--
OptionsGrid SystemGrid systemPARAMETERS_GRID_SYSTEM--
StandardizeBooleanSTANDARD-Default: 0
ScaleValue rangeRADIUSkernel radius in map units; defines an annulus if inner radius is greater than zero-
Weighting FunctionChoiceDW_WEIGHTING-Available Choices:
[0] no distance weighting
[1] inverse distance to a power
[2] exponential
[3] gaussian
Default: 0
PowerFloating pointDW_IDW_POWER-Minimum: 0.000000
Default: 2.000000
BandwidthFloating pointDW_BANDWIDTHBandwidth for exponential and Gaussian weightingMinimum: 0.000000
Default: 1.000000

Command-line

Usage: saga_cmd ta_morphometry 18 [-DEM <str>] [-TPI <str>] [-STANDARD <str>] [-RADIUS_MIN <double>] [-RADIUS_MAX <double>] [-DW_WEIGHTING <str>] [-DW_IDW_POWER <double>] [-DW_BANDWIDTH <double>]
  -DEM:<str>            	Elevation
	Grid, input
  -TPI:<str>            	Topographic Position Index
	Grid, output
  -STANDARD:<str>       	Standardize
	Boolean
	Default: 0
  -RADIUS_MIN:<double>  	Scale
	Value range
  -RADIUS_MAX:<double>  	Scale
	Value range
  -DW_WEIGHTING:<str>   	Weighting Function
	Choice
	Available Choices:
	[0] no distance weighting
	[1] inverse distance to a power
	[2] exponential
	[3] gaussian
	Default: 0
  -DW_IDW_POWER:<double>	Power
	Floating point
	Minimum: 0.000000
	Default: 2.000000
  -DW_BANDWIDTH:<double>	Bandwidth
	Floating point
	Minimum: 0.000000
	Default: 1.000000