Headings of the segments of a movement track

This function calculates the heading/azimuth/direction of movement of each segment between consecutive locations of a track.

Usage

# S4 method for .MoveTrackSingle
angle(x)
  # S4 method for .MoveTrackStack
angle(x)

Arguments

x: a move, moveStack or moveBurst object

Details

Other terms for this measurment are azimuth or direction of travel/movement. The angles are relative to the North pole. The headings are calculated using the functions bearing of the geosphere package.

Author

Marco Smolla & Anne Scharf

Value

Angles in degrees (between -180 and 180). North is represented by 0.

If a move object is provided, a numeric vector one element shorter than the number of locations is obtained.

If a moveStack object is provided, a list with one element per individual containing a numeric vector one element shorter than the number of locations is obtained.

Examples

## angles from a Move object 
data(leroy)
head(angle(leroy))
#> [1]  101.44448  157.41345   26.47859 -133.22121 -108.37639   72.45405
# to add this information to the move object, a "NA" has to be assigened
# e.g. to the last location (it also could be assigend to the first location).
leroy$angles <- c(angle(leroy), NA)

## angles from a MoveStack object
data(fishers)
str(angle(fishers))
#> List of 2
#>  $ Leroy  : num [1:918] 101.4 157.4 26.5 -133.2 -108.4 ...
#>  $ Ricky.T: num [1:999] 115.7 70.2 -18.2 -78.9 76.5 ...
# to add this information to the moveStack object, a "NA" has to be assigened
# e.g. to the last location of each individual
fishers$angles <- unlist(lapply(angle(fishers), c, NA))