r.tpicalculates a multiscale version of the Topographic Position Index (TPI) of Guisan et al. (1999). The TPI is calculated by averaging a DEM over a user-specified moving window size and subtracting the original DEM from the averaged version to get the residual. This has the effect of extracting finer-scale landforms from regional-scale relief. Positive TPI values represent ridges or hills, and negative TPI values represent valleys or pits.
Unlike the original TPI, r.tpi implements a multiscale version that calculates a standardized TPI over multiple neighborhood radii from minradius to maxradius, starting at the largest neighborhood size. For subsequent steps, the standardized TPI is updated with pixels where the absolute TPI values exceed the TPI values of the previous step. For large neighborhoods > 15, resampling is used rather than a focal function to generalize the DEM.
g.region raster=elevation@PERMANENT -a r.tpi input=elevation@PERMANENT minradius=1 maxradius=25 steps=5 output=tpi
Available at: r.tpi source code (history)
Latest change: Monday Jan 30 19:52:26 2023 in commit: cac8d9d848299297977d1315b7e90cc3f7698730
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