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

Guisan, A., Weiss, S.B., Weiss, A.D. (1999): GLM versus CCA spatial modeling of plant species distribution. Plant Ecology 143: 107-122.
Weiss, A.D. (2000): Topographic Position and Landforms Analysis. Poster http://www.jennessent.com/downloads/tpi-poster-tnc_18x22.pdf.
Wilson, J.P. & Gallant, J.C. (2000): Primary Topographic Attributes. In: Wilson, J.P. & Gallant, J.C. [Eds.]: Terrain Analysis: Principles and Applications, John Wiley & Sons, p.51-85.

Author: O.Conrad (c) 2011
Menu: Terrain Analysis|Morphometry

Parameters

	Name	Type	Identifier	Description	Constraints
Input	Elevation	Grid (input)	`DEM`	-	-
Output	Topographic Position Index	Grid (output)	`TPI`	-	-
Options	Grid system	Grid system	`PARAMETERS_GRID_SYSTEM`	-	-
	Standardize	Boolean	`STANDARD`	-	Default: 0
	Scale	Value range	`RADIUS`	kernel radius in map units	-
	Weighting Function	Choice	`DW_WEIGHTING`	-	Available Choices: [0] no distance weighting [1] inverse distance to a power [2] exponential [3] gaussian weighting Default: 0
	Inverse Distance Weighting Power	Floating point	`DW_IDW_POWER`	-	Minimum: 0.000000 Default: 1.000000
	Inverse Distance Offset	Boolean	`DW_IDW_OFFSET`	Calculates weights for distance plus one, avoiding division by zero for zero distances	Default: 1
	Gaussian and Exponential Weighting Bandwidth	Floating point	`DW_BANDWIDTH`	-	Minimum: 0.000000 Default: 75.000000

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_IDW_OFFSET <str>] [-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 weighting
	Default: 0
  -DW_IDW_POWER:<double>	Inverse Distance Weighting Power
	Floating point
	Minimum: 0.000000
	Default: 1.000000
  -DW_IDW_OFFSET:<str>  	Inverse Distance Offset
	Boolean
	Default: 1
  -DW_BANDWIDTH:<double>	Gaussian and Exponential Weighting Bandwidth
	Floating point
	Minimum: 0.000000
	Default: 75.000000