jppa: Joint Potential Path Area of Two Animals
In jedalong/wildlifeTG: Time Geograhic Analysis of Wildlife Telemetry Data

Description Usage Arguments Details Value References See Also

The function jppa computes the joint accessibility space between two animals. It can be used to map (as a spatial polygon) the area that could have been jointly accessed by two individual animals in space ant time. The jPPA represents a spatial measure of spatial-temporal interaction.

jppa(traj1, traj2, t.int = 0.1 *
  as.numeric(names(sort(-table(ld(traj1)$dt)))[1]),
  tol = max(ld(traj1)$dt, na.rm = T), dissolve = TRUE,
  proj4string = CRS(as.character(NA)), ePoints = 360, ...)

`traj1`	an object of the class `ltraj` which contains the time-stamped movement fixes of the first object. Note this object must be a `type II ltraj` object. For more information on objects of this type see `help(ltraj)`.
`traj2`	same as `traj1`.
`t.int`	(optional) time parameter (in seconds) used to determine the frequency of time slices used to delineate the joint activity space. Default is 1/10th of the mode of the temporal sampling interval from `traj1`. Smaller values for `t.int` will result in smoother output polygons.
`tol`	(optional) parameter used to filter out those segments where the time between fixes is overly large (often due to irregular sampling or missing fixes); which leads to an overestimation of the activity space via the PPA method. Default is the maximum sampling interval from `traj1`.
`dissolve`	logical parameter indicating whether (`=TRUE`; the default) or not (`=FALSE`) to return a spatially dissolved polygon of the joint activity space.
`proj4string`	a string object containing the projection information to be passed included in the output `SpatialPolygonsDataFrame` object. For more information see the `CRS-class` in the packages `sp` and `rgdal`. Default is `NA`.
`ePoints`	number of vertices used to construct each PPA ellipse. More points will necessarily provide a more detailed ellipse shape, but will slow computation; default is 360.
`...`	additional parameters to be passed to the function `dynvmax`. For example, should include options for `dynamic` and `method`; see the documentation for `dynvmax` for more detailed information on what to include here.

The function jppa can be used to map areas of potential interaction between two animals. Specifically, this represents a measure of spatial overlap that also considers the temporal sequencing of telemetry points. In this respect it improves significantly over static measures of home range overlap, often used to measure static interaction, and can be considered as a spatial measure of dynamic interaction.

This function returns a SpatialPolygonsDataFrame representing the joint accessibility space between the two animals.

Long, J.A., Webb, S.L., Nelson, T.A., Gee, K. (2015) Mapping areas of spatial-temporal overlap from wildlife telemetry data. Movement Ecology. 3:38.

dynvmax, dynppa

jedalong/wildlifeTG documentation built on July 17, 2019, 2:52 p.m.