This tools calculates a type of shape narrowness index (NI) for raster objects. The index is equal to:

> NI = A / (πMD2)

where A is the patch area and MD is the maximum distance-to-edge of the patch. Circular-shaped patches will have a narrowness index near 1.0, while more narrow patch shapes will have higher index values. The index may be conceptualized as the ratio of the patch area to the area of the largest contained circle, although in practice the circle defined by the radius of the maximum distance-to-edge will often fall outside the patch boundaries.

Objects in the input raster (`input`) are designated by their unique identifiers. Identifier values must be positive, non-zero whole numbers. It is quite common for identifiers to be set using the clump tool applied to some kind of thresholded raster.

## See Also

linearity_index, elongation_ratio, clump

## Function Signature

`def narrowness_index(self, raster: Raster) -> Raster: ...`

## Project Links

WbW Homepage User Manual Support WbW