[R-sig-Geo] Distance calculating between points according to a river network

[Mirza Cengic]

Hi Tristan,

I recently had to do something similar (calculating distance to the next
downstream point), and I was not able to find a solution with R that would
deal with the direction of the flow. Perhaps someone who has deeper
understanding of packages such as iGraph etc. might be able to find a
solution, but I wasn't.
I solved the problem with ArcMap, using HydroTools extension, where you
need to define a geometric network that has a direction, and then the
calculation is pretty straightforward with HydroTools (let me know if you
need more info).
I would prefer to have a scripted solution in an open-source software, but
this worked for me in any case. If anyone has a better way for solving
this, I would love to see how!

Cheers,
Mirza.

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