essie: Essie

In SWotherspoon/SGAT: Solar/Satellite Geolocation for Animal Tracking

Essie

Description

Fit an Essie model

Usage

essie(model, grid, epsilon1 = 0.001, epsilon2 = 1e-16, verbose = interactive())

Arguments

model	a model structure generated by essieThresholdModel.
grid	a raster object defining the grid
epsilon1	likelihood tolerance
epsilon2	transition probability tolerance.
verbose	report progress at prompt?

Details

Essie is a discrete analog of Stella that only considers locations on a lattice of grid points.

The posterior probability that the tag is at a particular location is determined by a two pass recursive algorithm. The forward sweep propogates location information forward in time, the backward sweep propogates location information backward in time, and the full posterior is a compromise of these two.

The method is only approximate and is controlled by the two tolerances epsilon1 and epsilon2. The first limits the precision of the likelihood - locations for which the likelihood fall below epsilon1 of its maximum are ignored. The second limits the precision of the transition probabilities - locations for which the probability below epsilon2 of the maximum are ignored in the movement calculation. The smaller these parameters are set, the slower but more accurate the fit.

Value

a list with elements

grid	a raster object that defines the grid.
times	the times corresponding to the location estimates.
lattice	a sparse grid representation of the posterior location probabilities.

SWotherspoon/SGAT documentation built on June 1, 2022, 10:49 p.m.