Distance calculating between points according to a river network

Hi,

I'm a R new user and this is also my first post on this mailing list.

I'm currently working on several project with R and I still have not found
a solution for one :

To be concise I'm working with shapefiles representing on a delimited area :

- sewage plant (SpatialPointsDataFrame)
- water quality measurement stations (SpatialPointsDataFrame)
- hydrographic network (SpatialLineDataFrame)

What I want to do is to calculate the distance between each sewage stations
and each measurement stations following the river route.

For now, I have snapped all my points on the river and created a new layer
with both type of point (sewage stations and measurement) in order to split
the lines by the point layer.

I'm looking for a way to get a kind of distance's matrix.

Does anybody has already worked on a similar project ? I'm kind of lost
with all the R packages and functions so any pistes or proposals or idea
will be greatly appreciate.


PS : As I said this is my first post. If I'm not clear about my issue or if
I'm not respecting any posting rules don't hesitate to tell me about.


Cheers

Tristan Bourgeois
Hydromorphologist
Water Agency of Seine-Normandie Basin

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