[GRASS-user] r.stream.extract - stream dir map output

[Markus Metz]

Jarosław Jasiewicz wrote:
> M S pisze:
>> As an output from r.streams.extract, I'm getting a stream direction
>> map that is only along the stream network, and null everywhere else.
>> >From the manual, it seems the direction map needs to be for the entire
>> study area.  I am looking to feed the streams and direction map into
>> the r.stream.basins module.
>>   Since I'm on GRASS 6.4RC5, I dont have MFD option in my r.watershed,
>> so I rely upon r.stream extract to output the stream network and the
>> direction map.  I had seen a portion in the notes stating "Nowadays f
>> direction map comes from r.stream.extract must be patched by direction
>> map from r.watershed. (with r.patch).
>>
>> I wouldnt think I could patch the SFD direction output from
>> r.watershed with the MFD stream direction map to create a direction
>> map for the entire study area.  Is there another solution to use MFD?
>>   
> if grass64 really do not have MFD (i'm suprised!) the only solution is 
> to compile grass 65 from source
grass64 has MFD in r.terraflow. You can use r.terraflow + 
r.dominant_dir.m + r.calc_terraflow_dir.m (grass-addons) in order to get 
the main drainage direction for MFD flow, use r.terraflow flow 
accumulation and the filled elevation map produced by r.terraflow as 
input to r.stream.extract, then patch the new flow directions into the 
main drainage direction extracted with the addon tools.

You can also use flow accumulation from r.watershed with SFD as input to 
r.stream.extract and patch the flow directions of r.stream.extract into 
r.watershed flow directions, these are compatible. But note ticket #807.

As Jarek said, best would be to use r.watershed in grass65 instead.

Hope that helps,

Markus M