[GRASS-user] Directed vector networks (e.g. river networks)

[Markus Metz]

On Fri, Jun 14, 2013 at 11:03 AM, Johannes Radinger
<johannesradinger at gmail.com> wrote:
> Hi,
>
> as I am not very familiar with GRASS' vector capabilities maybe someone of
> you has some ideas. Is there the concept of directed vector networks e.g
> describing river networks with flow direction implemented in GRASS?

r.stream.extract produces a vector network with the direction of the
lines corresponding to the flow direction.
>
> I am looking for a way that counts all barriers when routing from a starting
> point in the network And I'd like to get the number of barriers that are
> downstream and those that are upstream a given point. Or is there a way to
> "cut" a network into two parts where one is automatically detected as
> upstream while the other one is declared as the downstream network?

Maybe the linear referencing system can help to count barriers.

For separate upstream/downstream analysis, you could use vector
network analysis tools and make use of the line direction: if want to
go only upstream, set forward costs to -1, if you want to go only
downstream, set backward costs to -1.

>
> Furthermore I am interested in calculating stream order for such dendritic
> networks. I saw the v.strahler add on, is there also an add on that
> calculates other types of stream order (here I am most interested in a
> vector based Shreve's stream order like as already implemented in
> r.stream.order).

You could use r.stream.extract to produce both a raster and a vector
river network, then run r.stream.order on the river raster and update
the attributes of the vector with the desired order using v.what.rast.

HTH,

Markus M