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; defines an annulus if inner radius is greater than zero | - | |
| Weighting Function | choice | DW_WEIGHTING | - | Available Choices: [0] no distance weighting [1] inverse distance to a power [2] exponential [3] gaussian Default: 0 | |
| Power | floating point number | DW_IDW_POWER | - | Minimum: 0.000000 Default: 2.000000 | |
| Bandwidth | floating point number | DW_BANDWIDTH | Bandwidth for exponential and Gaussian weighting | Minimum: 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 number Minimum: 0.000000 Default: 2.000000 -DW_BANDWIDTH:<double> Bandwidth floating point number Minimum: 0.000000 Default: 1.000000