Retrieve each individual flightline by attributing a number to each point. The
function depends on the GPS time to retrieve each individual flightline. In a
continuous dataset, once points are ordered by GPS time, the time between two
consecutive points does not exceed a few milliseconds. If the time between two consecutive
points is too long it means that the second point is from a different flightline. The default
threshold is 30 seconds. A column 'flightlineID' is added in the slot @data
lasflightline(.las, dt = 30)A LAS object
numeric. The threshold time lag used to retrieve flightlines
Return nothing. The original object is modified in place by reference.