[R-sig-Geo] Measuring length of trajectories

[Michael Sumner]

On Thu, 24 May 2018 at 23:32 Jeri Wisman <jwism002 using odu.edu> wrote:

> Hi all -
>
> I am trying to measure the length of time of trajectories taken of seabird
> movements to be able to relate time of flight to distance of flight. Any
> suggestions of a function or package on how to measure the time? Thanks,
>

There are very many, including adehabitatLT package and the trackDistance
function in the trip package (I know how that one works so it's easy for me
to help with, but it's not as sophisticated as adehabitat family so
pros/cons).

Both packages requires you to get your data into the right format. There's
more general capability in sp::spDists which has arguments longlat (set to
TRUE for great circle distances from longlat) and segments, which gives
sequential paired distances. Both adehabitatLT and trip will handle the
grouping of locations into separate paths (ordered by time).

I'd say it's worth trying some of the purpose-built packages, because then
some of the metrics can be extracted very easily (once you know your way
around). Explore the "Moving objects, trajectories" section of this Task
View

https://gist.github.com/mdsumner/0a3cb0e58bf9d37b782943ac269e1eff

and this list of recentish additions, pending update to the Task View,
which gives a taste of how much activity there is in this space(!).

https://gist.github.com/mdsumner/0a3cb0e58bf9d37b782943ac269e1eff

Cheers, Mike.

>
> *Jeri Wisman* | Masters Candidate
> Old Dominion University
> Department of Biological Sciences
> Mills Godwin Building, Room 312
> Norfolk VA 23529 USA
>
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-- 
Dr. Michael Sumner
Software and Database Engineer
Australian Antarctic Division
203 Channel Highway
Kingston Tasmania 7050 Australia

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