interpolateTime {move}

Interpolate a trajectory

Description

This function allows to interpolate trajectories. It does this on the basis of a simple interpolation, depending on the spaceMethod that is specified.

Usage

interpolateTime(x, time, spaceMethod=c('euclidean','greatcircle','rhumbline'),...)

Arguments

x

a move or moveBurst object.

time

either a number of locations (class numeric), a time interval (class difftime) or a vector of timestamps (class POSIXct) at which the interpolation should be done. See 'Details'.

spaceMethod

a character that indicates the interpolation function (euclidean, great circle or along the rhumb line) to be used to generate the new locations.

...

Currently not implemented.

Details

In the argument time:
- number of locations: refer the total number of locations that the resulting track will have distributed equally over time. E.g. if time=200, the resulting track will have 200 points interpolated at a constant time interval.
- time interval: refers to the time interval at which a location should be interpolated. E.g. if time=as.difftime(10, units="mins") a location will be interpolated every 10 mins.
- vector of timestamps: the timestamps of this vector have to be in ascending order, and within the time range of the track.

Value

Move-class object of the interpolated locations.

Author(s)

Bart Kranstauber & Anne Scharf

Examples

data(leroy)
## providing the number of locations
plot(leroy[100:150,], col="red",pch=20)
points(mv <- interpolateTime(leroy[100:150,], time=500, spaceMethod='greatcircle'))

## providing a time interval
plot(leroy[100:150,], col="red",pch=20)
points(mv2 <- interpolateTime(leroy[100:150,], time=as.difftime(10, units="mins"), 
                              spaceMethod='greatcircle'))

## providing a vector of timestamps
plot(leroy[100:150,], col="red",pch=20)
ts <- as.POSIXct(c("2009-02-13 10:00:00", "2009-02-13 12:00:00", "2009-02-13 14:00:00",
                   "2009-02-13 16:00:00","2009-02-13 18:00:00","2009-02-13 20:00:00",
                   "2009-02-13 22:00:00","2009-02-14 00:00:00","2009-02-14 02:00:00",
                   "2009-02-14 04:00:00","2009-02-14 06:00:00", "2009-02-14 08:00:00", 
                   "2009-02-14 10:00:00"),  format="%Y-%m-%d %H:%M:%S", tz="UTC")
points(mv3 <- interpolateTime(leroy[100:150,], time=ts, spaceMethod='greatcircle'))