Let $latex C_s = \{c _1 , c_2 , …d_n \}$ be the
set of cells at scale $latex s$ where the occurrences of a node X where found. The $latex C _{s−1} = \{d_ 1 , d_ 2 , …d _k \}$ is
the corresponding set of cells at an upper scale (ancestor of $latex s $) where the occurrences of a node X where found.
Note that the ratio:
$latex r_s = \frac{\#C_{s-1}}{\#C_s}$
gives us an indicator of how the occurrences are dispersed in the space.
If $latex r_s$ is low means that the
spatial distribution is constrained in a region as small as the unit area of the upper scale while if $latex r_s$ is close to 1 it tells us that the occurrences are as spatially distributed as the cells in the upper scale.
The method can be applied recursively to the sucessive scales to obtain a list of ratios $latex r_1 , r_2 , ..r_s ,.. $ that can be fitted in model to estimate geographic extensions.