xrspatial.terrain_metrics.tpi#

xrspatial.terrain_metrics.tpi(agg: DataArray, name: str | None = 'tpi', boundary: str = 'nan') → DataArray[source]#

Compute the Topographic Position Index (TPI) for each cell.

TPI is the difference between the elevation of the center cell and the mean elevation of its 8 neighbors in a 3x3 window (Weiss 2001). Positive values indicate ridgetops, negative values indicate valleys, and near-zero values indicate flat areas or mid-slope positions.

Parameters:

agg (xarray.DataArray or xr.Dataset) – 2D NumPy, CuPy, NumPy-backed Dask, or CuPy-backed Dask xarray DataArray of elevation values. If a Dataset is passed, the operation is applied to each data variable independently.
name (str, default='tpi') – Name of output DataArray.
boundary (str, default='nan') – How to handle edges where the kernel extends beyond the raster. 'nan' - fill missing neighbours with NaN (default). 'nearest' - repeat edge values. 'reflect' - mirror at boundary. 'wrap' - periodic / toroidal.

Returns:

2D array of TPI values with the same shape, coords, dims, and attrs as the input.

Return type:

xarray.DataArray or xr.Dataset

References

Weiss, A. (2001). Topographic Position and Landforms Analysis. Poster presentation, International User Conference, San Diego, CA.