[GRASS-user] Stream flow direction map

[Jarek Jasiewicz]

Nikos Alexandris pisze:
> On Saturday 01 of May 2010 05:30:04 Nikos Alexandris wrote:
>   
>> I am sort of forwarding a friends question related to hydro-processing.
>>
>> While there is a proper (vector) contour map and a very clean stream
>> network map (digitised from scratch upon topographic maps of 1:50.000)
>> available, the flow direction map is missing.
>>
>> Is this information easily calculated based on available dem(s), stream
>> network(s)? Or should _definitely_ the user add this information while
>> digitising the streams?
>>
>> I have read many past threads wrt "streams, flow, direction, accumulation"
>> but could not trace an answer to the above question.
>>     
>
> I read again some stuff and I guess that this is a very basic and simple 
> "hydro-gis" question (for which I do not know the answer):
>
> is the direction map bound to a specific stream network, i.e. the one that 
> r.watershed or r.stream.extract produces  or  is it an independent one, based 
> solely on the input elevation model and its (x-y-z?) resolution?
>
> If the latter is true, then it only takes to use either r.watershed or 
> r.stream.extract to get the direction(s).
>
> If not, then the question is if the user can supply his own stream map to 
> r.stream.* modules (specifically to r.stream.extract) in order to get the 
> desired flow direction map?
>   
Interested question, but I think the easiest answer is carving or stream 
burining (r.stream.carve). Next reproduce r.watershed or 
r.stream.extract you shall receive (almost) ideally confidential network 
with supplied
HTH
Jarek
> Thanks, Nikos
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