Topographic Position Index (TPI)
- Author: O.Conrad (c) 2011
- Menu: Terrain Analysis | Morphometry
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.
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.
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: 75.000000 |
Command Line
Usage: saga_cmd ta_morphometry 18 [-DEM ] [-TPI ] [-STANDARD ] [-RADIUS_MIN ] [-RADIUS_MAX ] [-DW_WEIGHTING ] [-DW_IDW_POWER ] [-DW_BANDWIDTH ]
-DEM: Elevation
grid, input
-TPI: Topographic Position Index
grid, output
-STANDARD: Standardize
boolean
Default: 0
-RADIUS_MIN: Scale
value range
-RADIUS_MAX: Scale
value range
-DW_WEIGHTING: Weighting Function
choice
Available Choices:
[0] no distance weighting
[1] inverse distance to a power
[2] exponential
[3] gaussian
Default: 0
-DW_IDW_POWER: Power
floating point number
Minimum: 0.000000
Default: 2.000000
-DW_BANDWIDTH: Bandwidth
floating point number
Minimum: 0.000000
Default: 75.000000