## Description

This tool calculates the Yokoyama et al. (2002) topographic openness index from an input DEM (`input`). Openness has two viewer perspectives, which correspond with positive and negative openness outputs (`pos_output` and `neg_output`). Positive values, expressing openness above the surface, are high for convex forms, whereas negative values describe this attribute below the surface and are high for concave forms. Openness is an angular value that is an average of the horizon angle in the eight cardinal directions to a maximum search distance (`dist`), measured in grid cells. Openness rasters are best visualized using a greyscale palette.

Positive Openness:

Negative Openness:

## References

Yokoyama, R., Shirasawa, M., & Pike, R. J. (2002). Visualizing topography by openness: a new application of image processing to digital elevation models. Photogrammetric engineering and remote sensing, 68(3), 257-266.

## See Also

viewshed, horizon_angle, time_in_daylight, hillshade

## Function Signature

`def openness(self, dem: Raster, dist: int = 20) -> Tuple[Raster, Raster]: ...`

## Project Links

WbW Homepage User Manual Support WbW