[GRASS-user] Merging connected stream lines

Huidae Cho grass4u at gmail.com
Sat Oct 28 06:18:54 PDT 2017


BTW, let me understand weakly vs strongly connected components generated by
v.net.components.

Strongly connected: All paths between nodes u and v should have the same
direction.

Weakly connected: Only requires "connections" between nodes u and v, and
their directions don't matter.

If my understanding is correct, a stream vector map generated by thinning
and converting the stream raster map (flow directions not guaranteed) to
vector would only be weakly connected.

The stream vector output from r.streams.extract would be both strongly and
weakly connected because it honors flow directions.

Please let me know if I'm mistaken.

Thanks.
Huidae



On Sat, Oct 28, 2017 at 9:06 AM, Huidae Cho <grass4u at gmail.com> wrote:

> It's working great! Thanks for the quick implementation. It will help a
> lot!
>
> Huidae
>
> On Fri, Oct 27, 2017 at 3:58 PM, Markus Metz <
> markus.metz.giswork at gmail.com> wrote:
>
>>
>>
>> On Fri, Oct 27, 2017 at 2:38 PM, Huidae Cho <grass4u at gmail.com> wrote:
>> >
>> > [...] I tried your r.stream.extract to extract stream lines and its
>> output makes much more sense. It would be great if this module also outputs
>> unique stream "network" numbers.
>>
>> Unique stream network numbers are added as new attribute "network" in
>> trunk r71599.
>>
>> Markus M
>> >
>> > Thanks.
>> > Huidae
>> >
>> >
>> > On Fri, Oct 27, 2017 at 8:14 AM, Markus Metz <
>> markus.metz.giswork at gmail.com> wrote:
>> >>
>> >>
>> >>
>> >> On Fri, Oct 27, 2017 at 12:52 PM, Huidae Cho <grass4u at gmail.com>
>> wrote:
>> >> >
>> >> > Actually, I'm getting the same error as Markus in the NC dataset. I
>> recently discleaned and rebuilt the latest SVN.
>> >>
>> >> In trunk, this bug appeared with r71267 and was fixed with r71477.
>> >> In relbr72, this bug appeared with r71268 and was fixed with r71478.
>> >>
>> >> Please check your revision.
>> >>
>> >> Markus M
>> >>
>> >> >
>> >> > Huidae
>> >> >
>> >> > On Thu, Oct 26, 2017 at 4:14 PM, Markus Metz <
>> markus.metz.giswork at gmail.com> wrote:
>> >> >>
>> >> >>
>> >> >>
>> >> >> On Thu, Oct 26, 2017 at 5:02 PM, Markus Neteler <neteler at osgeo.org>
>> wrote:
>> >> >> >
>> >> >> > On Thu, Oct 26, 2017 at 9:58 AM, Stefan Blumentrath
>> >> >> > <Stefan.Blumentrath at nina.no> wrote:
>> >> >> > > Hi,
>> >> >> > >
>> >> >> > > Did you try:
>> >> >> > >
>> >> >> > > https://grass.osgeo.org/grass72/manuals/v.net.components.html
>> >> >> > >
>> >> >> > > That might give you a common attribute for all connected lines
>> in your
>> >> >> > > network…
>> >> >> >
>> >> >> > I just tried that with NC but:
>> >> >> >
>> >> >> > GRASS 7.3.svn (nc_spm_08_grass7):~ > v.net.components
>> input=roadsmajor
>> >> >> > output=roadsmajor_components method=strong
>> >> >> > Building graph...
>> >> >> > Registering arcs...
>> >> >> >  100%
>> >> >> > Flattening the graph...
>> >> >> > ERROR: GngFlatten error
>> >> >> >
>> >> >> >
>> >> >> > GRASS 7.3.svn (nc_spm_08_grass7):~ > v.net.components
>> input=railroads
>> >> >> > output=railroads_components method=strong
>> >> >> > Building graph...
>> >> >> > Registering arcs...
>> >> >> >  100%
>> >> >> > Flattening the graph...
>> >> >> > ERROR: GngFlatten error
>> >> >> >
>> >> >> > Does the network need any special treatment?
>> >> >>
>> >> >> I can not reproduce these errors. Please update your local copy:
>> >> >> make distclean
>> >> >> svn --no-ignore status
>> >> >> svn up
>> >> >> configure
>> >> >> make
>> >> >>
>> >> >> Markus M
>> >> >> >
>> >> >> > Markus
>> >> >> > _______________________________________________
>> >> >> > grass-user mailing list
>> >> >> > grass-user at lists.osgeo.org
>> >> >> > https://lists.osgeo.org/mailman/listinfo/grass-user
>> >> >>
>> >> >>
>> >> >> _______________________________________________
>> >> >> grass-user mailing list
>> >> >> grass-user at lists.osgeo.org
>> >> >> https://lists.osgeo.org/mailman/listinfo/grass-user
>> >> >
>> >> >
>> >
>> >
>>
>
>
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