dynppa: Dynamic PPA Measure of Animal Space Use

In jedalong/wildlifeTG: Time Geograhic Analysis of Wildlife Telemetry Data

Description

The function dynppa computes the (dynamic) PPA measure of the accessibility space of an animal. The PPA method can be thought as an alternative view on the home range; one that explicitly considers the spatial and temporal constraints on movement given known telemetry fixes, and a (dynamic) measure of maximum mobility - termed Vmax. The PPA method incorporates dynamic behaviour into the calculation of the vmax parameter used to delineate the original version of the PPA method, but the original method is still an option here.

Usage

dynppa(traj, tol = max(ld(traj)$dt, na.rm = TRUE), dissolve = TRUE,
  proj4string = CRS(as.character(NA)), ePoints = 360, ...)

Arguments

traj	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).
tol	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 traj.
dissolve	(logical) whether or not to dissolve output elliplse polygons to create a single output polygon, or keep the individual segment PPA ellipses. Default = TRUE.
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 method and/or dynamic parameters, see the documentation for dynvmax for more detailed information on what to include here.

Details

The function dyn.ppa represents an extension to an existing PPA method (Long and Nelson, 2012). Dynamic calculation of the PPA method improves upon the original version by flexibly modelling the vmax parameter according to wildlife behaviour. See the function dyn.vmax for more information on how to incorporate dynamic behaviour into the vmax parameter estimation.

Value

This function returns a SpatialPolygonsDataFrame representing the dynamic PPA measure of the accessibility space of an individual animal.

References

Long, JA, Nelson, TA. (2012) Time geography and wildlife home range delineation. Journal of Wildlife Management, 76(2):407-413.

Long, JA, Nelson, TA. (2014) Home range and habitat analysis using dynamic time geography. Journal of Wildlife Management. Accepted: 2014-12-03.

See Also

dynvmax

Examples

data(m3)
ppa1 <- dynppa(m3,method='vanderWatt')
ppa2 <- dynppa(m3,method='vanderWatt',dynamic='focal')
sp::plot(ppa1)
sp::plot(ppa2,add=TRUE,border='red')

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