Kernel Home Range Estimation for ArcGIS, using VBA - Fish and ...

(green radius of the blue search area in Figure 4.1.2.b.). The distance from each point (within the
search radius) to the evaluation point is then calculated (Figure 4.1.2.c.). Based on these
distances, a cumulative value is assigned to the evaluation point. Next, another evaluation point
is selected (Figure 4.1.3.a.). This procedure continues until all the points in the distribution have
been evaluated. They are all scored and assigned density values (denoted by classified
symbology in Figure 4.1.3.b.). A grid of specified size is then overlaid on the distribution (Figure
4.1.3.c.). Starting again with each evaluation point (red), the pixels within the search radius are
populated with (assigned) their respective density values (Figures 4.1.4.a. and 4.1.4.b.). Each
subsequent point is evaluated in the distribution (Figure 4.1.4.c.). Thus two processes are
occuring: first a point to point evaluation and then a pixel to point evaluation.
a b c
Figure 4.1.2. Process of finding points in a distribution (yellow points) that will contribute to the
density estimate at an evaluation point (red point). The area searched (blue circle) is
determined by the smoothing parameter, h (green line).
a b c
Figure 4.1.3. The procedure for generating density estimates continues from point to point in the
distribution (yellow points) until all locations have a density value (high density in black, to low
density in grey; white indicates zero density). Overlaying a grid is the next step towards
building a density surface.
12