This tool calculates the tangential curvature, which is the curvature of an inclined plan perpendicular to both the direction of flow and the surface (Gallant and Wilson, 2000). Curvature is a second derivative of the topographic surface defined by a digital elevation model (DEM). The user must input a DEM (`dem`). The output reports curvature in degrees multiplied by 100 for easier interpretation, as curvature values are often very small. The Z Conversion Factor (`zfactor`) is only important when the vertical and horizontal units are not the same in the DEM. When this is the case, the algorithm will multiply each elevation in the DEM by the Z Conversion Factor. If the DEM is in the geographic coordinate system (latitude and longitude), with XY units measured in degrees, an appropriate Z Conversion Factor is calculated internally based on site latitude.

## Reference

Gallant, J. C., and J. P. Wilson, 2000, Primary topographic attributes, in Terrain Analysis: Principles and Applications, edited by J. P. Wilson and J. C. Gallant pp. 51-86, John Wiley, Hoboken, N.J.

plan_curvature, profile_curvature, total_curvature, slope, aspect

## Function Signature

`def tangential_curvature(self, dem: Raster, log_transform: bool = False, z_factor: float = 1.0) -> Raster: ...`

## Project Links

WbW Homepage User Manual Support WbW