interpolate.ais.data {DEPONS2R} | R Documentation |
Interpolate AIS data
Description
Interpolates ship movement tracks obtained from Automatic Identification System (AIS) data to obtain exactly one position per 30 minutes. The first and last position in the original track are omitted unless minutes = 0 or 30 and seconds = 0.
Usage
interpolate.ais.data(aisdata)
Arguments
aisdata |
Data frame including the columns 'id' (ship identifier),
'time' (text string readable by |
Value
Returns a data frame with the same columns as the input data
See Also
read.DeponsShips
and ais.to.DeponsShips
Examples
data(aisdata)
ais.testdata <- aisdata[c(12,14,16) ,]
plot(ais.testdata[c("x", "y")], asp=1, col="green", pch=16, xlim=c(780000, 837000))
lines(ais.testdata[c("x", "y")])
# Add 600 sec to 'time' to mis-allign with intervcal needed
ais.testdata$time <- format(as.POSIXlt(ais.testdata$time)+600)
text(ais.testdata[c("x", "y")]-900, ais.testdata$time, adj=0, cex=0.5)
interpolated <- interpolate.ais.data(ais.testdata)
points(interpolated[,c("x", "y")], col="red")
text(interpolated[c("x", "y")]-900, interpolated$time, adj=0, cex=0.5)
legend("bottomright", bty="n", pch=c(16, 1), col=c("green", "red"),
legend=c("original positions", "interpolated"))
[Package DEPONS2R version 1.2.3 Index]