Local convex hull
LoCoH (Local Convex Hull) is a method for estimating the size of an animal's homerange and for constructing a probability distribution, referred to as the utilization distribution, that represents the probabilities of finding an animal within a given area of its (homeranges) at any point in time or at points in time for which the utilization distribution has been constructed (e.g. different utilization distributions can be constructed from data pertaining to particular periods of a diurnal or seasonal cycle). A utilization distribution is generally constructed from data providing the location of an individual in space at different points in time.
- Locate the k-1 nearest neighbors for each point in the dataset.
- Construct a convex hull for each set of nearest neighbors and the original data point.
- Merge these hulls together from smallest to largest.
- Divide the merged hulls into isopleths where the 10% isopleth contains 10% of the original data points, the 100% isopleth contains all the points, etc.
The LoCoH method has a number of strong points:
- It generates a density distribution denoting.
- As more data is added, the homerange becomes more accurate.
- It is handles 'sharp' features such as lakes and fences well.
- The generated homerange has a finite region.
LoCoH has a number of implementations including a LoCoH Web Application.
LoCoH was formerly known as k-NNCH, for k-Nearest Neighbor Convex Hulls.
See also
References
Getz, W. and C. Wilmers. 2004. A local nearest-neighbor convex-hull construction of home ranges and utilization distributions. Ecography 27: 489-505. View PDF
Getz, W.M, S. Fortmann-Roe, P. C. Cross, A. J. Lyonsa, S. J. Ryan, C.C. Wilmers, in review. LoCoH: nonparametric kernel methods for constructing home ranges and utilization distributions. View PDF