I am currently conducting a 'First Passage Time' (fpt) animal movement
analysis, in order to identify ARS zones from GPS tracks.

The study species in question frequently rests on the water surface during
darkness hours.  To avoid artificial inflation of fpt, I have removed these
points and have used the variance in the log of fpt to identify scales of
ARS behaviour within each of these track sub-sets. This has worked for
smaller-scale ARS zones, but not larger scales, owing to the separation of
each trip into daylight-only sections.

I would like to assign a constant speed to the whole trajectory for each
bird and then conduct a fpt analysis on the whole trajectory, to get an
indication of larger-scale ARS.

Could anyone recommend a function that could be used to rediscretize an
animal trajectory to constant speed?

I've tried redisltraj() from package adehabitatLT to rediscretize step
length at a constant interval, and then setNA() followed by sett0() to
create constant time interval, but this results in a lot of NAs in x/y,
which then seems to constain the fpt analysis.

Is there a better way to assign constant speed to the whole trajectory?

Any advice much appreciated.

Kylie Scales
Postgraduate Researcher
Plymouth Marine Laboratory

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