sma: Slow movement areas

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

Description

The function sma computes the areas representing slow movement areas as described in the paper Nelson et al. (2014). Slow movement areas represent areas of sustained or intense habitat use, related to slow movement behaviours. Slow movement areas are defined by counting consecutive fixes within time geographic ellipses, and represented spatially as spatial polygons that are the union of included telemetry fixes within the slow movement area.

Usage

sma(traj, sma.keep = 1, sma.tol = 1, tol = max(ld(traj)$dt, na.rm =
  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 animal. Note this object must be a type II ltraj object. For more information on objects of this type see help(ltraj).
sma.keep	an integer value indicating the number of slow movement areas to delineate, default is 1.
sma.tol	a value <= 1 indicating used when sma.keep > 1 to define how much overlap is allowed between SMA's, if sma.tol=1 no overlap is allowed, if sma.tol=0, any and all overlap is allowed. Typically something in between is most useful. Defaults to 1.
tol	(optional) parameter used to filter out those segments where the time between fixes is overly large (often due to missing fixes); which leads to an overestimation of the activity space via the PPA method. Default is the maximum sampling interval from traj1.
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.

Details

The function sma can be used to map slow movement areas identifiable from wildlife telemetry data.of potential interaction between two animals. Slow movement areas can be ranked, according to their importance, which equates to consecutive time spent in an area. That is, the first slow movement area will be the area where the animal stayed the longest, and so on. Thus, slow movement areas can be useful for identifying where encamped behaviour or intensively exploited habitat on the landscape.

Value

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

References

Nelson, T.A., Long, J.A., Laberee, K., Stewart, B.P. (2015) A time geographic approach for delineating areas of sustained wildlife use. Annals of GIS. 21(1): 81-90.

See Also

dynvmax, dynppa

Examples

data(m3)
sm1 <- sma(m3,method='vanderWatt')
sm2 <- sma(m3,sma.keep=2,method='vanderWatt')

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