pij = perimeter (m) of patch ij.
aij = area (m2) of patch ij.
Description FRAC equals 2 times the logarithm of patch perimeter (m) divided by the logarithm of patch area (m2); the perimeter is adjusted to correct for the raster bias in perimeter.
Units None
Range 1 ≦ FRAC ≦ 2
A fractal dimension greater than 1 for a 2-dimensional patch indicates a departure from Euclidean geometry (i.e., an increase in shape complexity). FRAC approaches 1 for shapes with very simple perimeters such as squares, and approaches 2 for shapes with highly convoluted, plane-filling perimeters.
Comments Fractal dimension index is appealing because it reflects shape complexity across a range of spatial scales (patch sizes). Thus, like the Shape index (SHAPE), it overcomes one of the major limitations of the straight perimeter-area ratio as a measure of shape complexity.