Mapping wildlife contacts

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Description

The function contacts is a simple function for mapping where wildlife contacts occur on the landscape with wildilfe telemetry data.

Usage

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contacts(traj1, traj2, dc = 0, tc = 0,
  proj4string = CRS(as.character(NA)))

Arguments

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.

tc

time threshold for determining simultaneous fixes – see function: GetSimultaneous.

dc

distance tolerance limit (in appropriate units) for defining when two fixes are spatially together.

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.

Details

The function contacts can be used to map where contacts occur on the lansdcape, contacts being defined spatially based on a distance threshold dc and temporally based on the time threshold tc – see the function getsimultaneous. The location of the contact is calculated as the midpoint between the two fixes that are determined to be a "contact" based on dc and tc.

Value

A SpatialPointsDataFrame containing the locations of the contacts. The time of the contact is stored in the attributes of the SpatialPointsDataFrame object, along with the actual distance between fixes.

See Also

GetSimultaneous, Prox

Examples

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data(deer)
deer37 <- deer[1]
deer38 <- deer[2]
#tc = 7.5 minutes, dc = 50 meters
spts <- contacts(deer37, deer38, tc=7.5*60, dc=50)