On Fri, Jun 14, 2013 at 11:59 AM, Markus Metz <[email protected] > wrote:
> On Fri, Jun 14, 2013 at 11:03 AM, Johannes Radinger > <[email protected]> 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. > Thank your for that info. I am totally unfamiliar with the LRS system, so I'll look into that and do some reading... :) > > 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. > > What tool of vector network analysis tool are you thinking of? can you given an example, e.g. to extract the enitre network upstream a given point? > > > > 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. > Yes I also thought of using the really nice r.stream.* toolbox, although it is somehow inconvinient to transform to and from raster/vector just to get the network topological factor "stream order". Theoretically, from a directed e.g. stream network that does not include "cycles" it should be possible to generate a stream order map, but probably that needs quite some knowledge abouot GRASS' network system and programming skills. Maybe a future add-on :) /Johannes > HTH, > > Markus M >
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