Re: [GRASS-user] Merging connected stream lines

[Huidae Cho]

I studied strongly vs. weakly connected components little bit. So...

1. As long as there are positive costs in both arc_column and
arc_backward_column between nodes, they are in the same strongly connected
components.
2. If any of arc_column and arc_backward_column is positive between nodes,
they are in the same weakly connected components.
3. If both columns are negative between two nodes, they are disconnected
even if there is a line between them.
4. Because of point 3 above, using and not using both columns may result in
different weakly connected components. No connected lines vs. no traversal
using a negative cost with connected lines.

Hope my understanding is correct.

Thank you.
Huidae


On Sun, Oct 29, 2017 at 12:07 PM, Markus Metz  wrote:

>
>
> On Sat, Oct 28, 2017 at 3:18 PM, Huidae Cho  wrote:
> >
> > 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.
>
> From the manual:
> "there are directed paths from u to v and from v to u"
>
> You can create directed graphs by assigning costs according to line
> direction with the arc_column and arc_backward_column options. The forward
> or backward direction of a line can be closed by setting costs to -1.
>
> By default, (no cost columns given), line lengths are used as costs,
> ignoring line direction because 1) line direction can be arbitrary, 2)
> typically lines can be traversed in both directions.
>
> Therefore, method=strong only makes sense if both arc_column and
> arc_backward_column are given and if some lines are closed in one
> direction. Otherwise, strong and weak will give the same results.
> >
> > Weakly connected: Only requires "connections" between nodes u and v, and
> their directions don't matter.
>
> To be precise, u must be reachable from v or v must be reachable from u.
> >
> > 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.
>
> Different stream networks are always different components. If you use
> arc_backward_column and close backward traversal, each stream network is
> again broken up into various strongly connected components.
>
> If you use r.thin + r.to.vect + arc_backward_column, a single stream
> network might even be broken up into several weakly connected components.
>
> HTH,
>
> Markus M
> >
> > Please let me know if I'm mistaken.
> >
> > Thanks.
> > Huidae
> >
> >
> >
> > On Sat, Oct 28, 2017 at 9:06 AM, Huidae Cho  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.gisw...@gmail.com> wrote:
> >>>
> >>>
> >>>
> >>> On Fri, Oct 27, 2017 at 2:38 PM, Huidae Cho  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.gisw...@gmail.com> wrote:
> >>> >>
> >>> >>
> >>> >>
> >>> >> On Fri, Oct 27, 2017 at 12:52 PM, Huidae Cho 
> 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.gisw...@gmail.com> wrote:
> >>> >> >>
> >>> >> >>
> >>> >> >>
> >>> >> >> On Thu, Oct 26, 2017 at 5:02 PM, Markus Neteler <
> nete...@osgeo.org> wrote:
> >>> >> >> >
> >>> >> >> > On Thu, Oct 26, 2017 at 9:58 AM, Stefan Blumentrath
> >>> >> >> >  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 

Re: [GRASS-user] Merging connected stream lines

[Markus Metz]

On Sat, Oct 28, 2017 at 3:18 PM, Huidae Cho  wrote:
>
> 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.

>From the manual:
"there are directed paths from u to v and from v to u"

You can create directed graphs by assigning costs according to line
direction with the arc_column and arc_backward_column options. The forward
or backward direction of a line can be closed by setting costs to -1.

By default, (no cost columns given), line lengths are used as costs,
ignoring line direction because 1) line direction can be arbitrary, 2)
typically lines can be traversed in both directions.

Therefore, method=strong only makes sense if both arc_column and
arc_backward_column are given and if some lines are closed in one
direction. Otherwise, strong and weak will give the same results.
>
> Weakly connected: Only requires "connections" between nodes u and v, and
their directions don't matter.

To be precise, u must be reachable from v or v must be reachable from u.
>
> 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.

Different stream networks are always different components. If you use
arc_backward_column and close backward traversal, each stream network is
again broken up into various strongly connected components.

If you use r.thin + r.to.vect + arc_backward_column, a single stream
network might even be broken up into several weakly connected components.

HTH,

Markus M
>
> Please let me know if I'm mistaken.
>
> Thanks.
> Huidae
>
>
>
> On Sat, Oct 28, 2017 at 9:06 AM, Huidae Cho  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.gisw...@gmail.com> wrote:
>>>
>>>
>>>
>>> On Fri, Oct 27, 2017 at 2:38 PM, Huidae Cho  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.gisw...@gmail.com> wrote:
>>> >>
>>> >>
>>> >>
>>> >> On Fri, Oct 27, 2017 at 12:52 PM, Huidae Cho 
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.gisw...@gmail.com> wrote:
>>> >> >>
>>> >> >>
>>> >> >>
>>> >> >> On Thu, Oct 26, 2017 at 5:02 PM, Markus Neteler 
wrote:
>>> >> >> >
>>> >> >> > On Thu, Oct 26, 2017 at 9:58 AM, Stefan Blumentrath
>>> >> >> >  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@lists.osgeo.org
>>> >> >> > https://lists.osgeo.org/mailman/listinfo/grass-user
>>> >> >>
>>> >> >>
>>> >> >> 

Re: [GRASS-user] Merging connected stream lines

[Huidae Cho]

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  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.gisw...@gmail.com> wrote:
>
>>
>>
>> On Fri, Oct 27, 2017 at 2:38 PM, Huidae Cho  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.gisw...@gmail.com> wrote:
>> >>
>> >>
>> >>
>> >> On Fri, Oct 27, 2017 at 12:52 PM, Huidae Cho 
>> 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.gisw...@gmail.com> wrote:
>> >> >>
>> >> >>
>> >> >>
>> >> >> On Thu, Oct 26, 2017 at 5:02 PM, Markus Neteler 
>> wrote:
>> >> >> >
>> >> >> > On Thu, Oct 26, 2017 at 9:58 AM, Stefan Blumentrath
>> >> >> >  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@lists.osgeo.org
>> >> >> > https://lists.osgeo.org/mailman/listinfo/grass-user
>> >> >>
>> >> >>
>> >> >> ___
>> >> >> grass-user mailing list
>> >> >> grass-user@lists.osgeo.org
>> >> >> https://lists.osgeo.org/mailman/listinfo/grass-user
>> >> >
>> >> >
>> >
>> >
>>
>
>
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Re: [GRASS-user] Merging connected stream lines

[Huidae Cho]

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 
wrote:

>
>
> On Fri, Oct 27, 2017 at 2:38 PM, Huidae Cho  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.gisw...@gmail.com> wrote:
> >>
> >>
> >>
> >> On Fri, Oct 27, 2017 at 12:52 PM, Huidae Cho  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.gisw...@gmail.com> wrote:
> >> >>
> >> >>
> >> >>
> >> >> On Thu, Oct 26, 2017 at 5:02 PM, Markus Neteler 
> wrote:
> >> >> >
> >> >> > On Thu, Oct 26, 2017 at 9:58 AM, Stefan Blumentrath
> >> >> >  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@lists.osgeo.org
> >> >> > https://lists.osgeo.org/mailman/listinfo/grass-user
> >> >>
> >> >>
> >> >> ___
> >> >> grass-user mailing list
> >> >> grass-user@lists.osgeo.org
> >> >> https://lists.osgeo.org/mailman/listinfo/grass-user
> >> >
> >> >
> >
> >
>
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Re: [GRASS-user] Merging connected stream lines

[Markus Metz]

On Fri, Oct 27, 2017 at 2:38 PM, Huidae Cho  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.gisw...@gmail.com> wrote:
>>
>>
>>
>> On Fri, Oct 27, 2017 at 12:52 PM, Huidae Cho  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.gisw...@gmail.com> wrote:
>> >>
>> >>
>> >>
>> >> On Thu, Oct 26, 2017 at 5:02 PM, Markus Neteler 
wrote:
>> >> >
>> >> > On Thu, Oct 26, 2017 at 9:58 AM, Stefan Blumentrath
>> >> >  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@lists.osgeo.org
>> >> > https://lists.osgeo.org/mailman/listinfo/grass-user
>> >>
>> >>
>> >> ___
>> >> grass-user mailing list
>> >> grass-user@lists.osgeo.org
>> >> https://lists.osgeo.org/mailman/listinfo/grass-user
>> >
>> >
>
>
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Re: [GRASS-user] Merging connected stream lines

[Markus Neteler]

v.net.componentsOn Fri, Oct 27, 2017 at 2:14 PM, Markus Metz
 wrote:
> On Fri, Oct 27, 2017 at 12:52 PM, Huidae Cho  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.

Yeah, my local copy was outdated (... /me travelling :-) - all fine
with v.net.components! Sorry for the noise.

thanks
markusN
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Re: [GRASS-user] Merging connected stream lines

[Huidae Cho]

Cool, just updated my repository and it's now working. I'll have to see the
output to understand what I can do with it.

Thanks.
Huidae

On Fri, Oct 27, 2017 at 8:38 AM, Huidae Cho  wrote:

> I'll check my revision. Thanks for the info.
>
> Also, I found that thinning the stream raster from r.watershed and
> converting it to vector doesn't really work well. When there are clumps of
> raster cells, flow directions get messed up. 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.
>
> Thanks.
> Huidae
>
>
> On Fri, Oct 27, 2017 at 8:14 AM, Markus Metz <
> markus.metz.gisw...@gmail.com> wrote:
>
>>
>>
>> On Fri, Oct 27, 2017 at 12:52 PM, Huidae Cho  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.gisw...@gmail.com> wrote:
>> >>
>> >>
>> >>
>> >> On Thu, Oct 26, 2017 at 5:02 PM, Markus Neteler 
>> wrote:
>> >> >
>> >> > On Thu, Oct 26, 2017 at 9:58 AM, Stefan Blumentrath
>> >> >  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@lists.osgeo.org
>> >> > https://lists.osgeo.org/mailman/listinfo/grass-user
>> >>
>> >>
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Re: [GRASS-user] Merging connected stream lines

[Huidae Cho]

I'll check my revision. Thanks for the info.

Also, I found that thinning the stream raster from r.watershed and
converting it to vector doesn't really work well. When there are clumps of
raster cells, flow directions get messed up. 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.

Thanks.
Huidae


On Fri, Oct 27, 2017 at 8:14 AM, Markus Metz 
wrote:

>
>
> On Fri, Oct 27, 2017 at 12:52 PM, Huidae Cho  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.gisw...@gmail.com> wrote:
> >>
> >>
> >>
> >> On Thu, Oct 26, 2017 at 5:02 PM, Markus Neteler 
> wrote:
> >> >
> >> > On Thu, Oct 26, 2017 at 9:58 AM, Stefan Blumentrath
> >> >  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@lists.osgeo.org
> >> > https://lists.osgeo.org/mailman/listinfo/grass-user
> >>
> >>
> >> ___
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> >
> >
>
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Re: [GRASS-user] Merging connected stream lines

[Stefan Blumentrath]

Hi,

It works fine for me:

GRASS 7.2.1svn (nc_spm_08_grass7): > v.net.components input=roadsmajor 
output=roadsmajor_components method=strong
Building graph...
Registering arcs...
100%
Flattening the graph...
Graph was built
Computing strongly connected components...
Writing output...
100%
Building topology for vector map
<roadsmajor_components@stefan.blumentrath>...
Registering primitives...
355 primitives registered
55717 vertices registered
Building areas...
100%
0 areas built
0 isles built
Attaching islands...
Attaching centroids...
100%
Number of nodes: 266
Number of primitives: 355
Number of points: 0
Number of lines: 355
Number of boundaries: 0
Number of centroids: 0
Number of areas: 0
Number of isles: 0
v.net.components complete. Found 7 components.

On:
GRASS 7.2.1svn (nc_spm_08_grass7): > g.version -g
version=7.2.1svn
date=2017
revision=r70326
build_date=2017-01-10
build_platform=x86_64-pc-linux-gnu
build_off_t_size=8

Cheers
Stefan

From: grass-user [mailto:grass-user-boun...@lists.osgeo.org] On Behalf Of 
Huidae Cho
Sent: fredag 27. oktober 2017 12.52
To: Markus Metz <markus.metz.gisw...@gmail.com>
Cc: GRASS user list <grass-user@lists.osgeo.org>
Subject: Re: [GRASS-user] Merging connected stream lines

Actually, I'm getting the same error as Markus in the NC dataset. I recently 
discleaned and rebuilt the latest SVN.
Huidae

On Thu, Oct 26, 2017 at 4:14 PM, Markus Metz 
<markus.metz.gisw...@gmail.com<mailto:markus.metz.gisw...@gmail.com>> wrote:


On Thu, Oct 26, 2017 at 5:02 PM, Markus Neteler 
<nete...@osgeo.org<mailto:nete...@osgeo.org>> wrote:
>
> On Thu, Oct 26, 2017 at 9:58 AM, Stefan Blumentrath
> <stefan.blumentr...@nina.no<mailto:stefan.blumentr...@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
> ___
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> https://lists.osgeo.org/mailman/listinfo/grass-user

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Re: [GRASS-user] Merging connected stream lines

[Markus Metz]

On Fri, Oct 27, 2017 at 12:52 PM, Huidae Cho  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.gisw...@gmail.com> wrote:
>>
>>
>>
>> On Thu, Oct 26, 2017 at 5:02 PM, Markus Neteler 
wrote:
>> >
>> > On Thu, Oct 26, 2017 at 9:58 AM, Stefan Blumentrath
>> >  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@lists.osgeo.org
>> > https://lists.osgeo.org/mailman/listinfo/grass-user
>>
>>
>> ___
>> grass-user mailing list
>> grass-user@lists.osgeo.org
>> https://lists.osgeo.org/mailman/listinfo/grass-user
>
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Re: [GRASS-user] Merging connected stream lines

[Huidae Cho]

Actually, I'm getting the same error as Markus in the NC dataset. I
recently discleaned and rebuilt the latest SVN.

Huidae

On Thu, Oct 26, 2017 at 4:14 PM, Markus Metz 
wrote:

>
>
> On Thu, Oct 26, 2017 at 5:02 PM, Markus Neteler  wrote:
> >
> > On Thu, Oct 26, 2017 at 9:58 AM, Stefan Blumentrath
> >  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@lists.osgeo.org
> > https://lists.osgeo.org/mailman/listinfo/grass-user
>
>
> ___
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> grass-user@lists.osgeo.org
> https://lists.osgeo.org/mailman/listinfo/grass-user
>
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Re: [GRASS-user] Merging connected stream lines

[Markus Metz]

On Thu, Oct 26, 2017 at 5:02 PM, Markus Neteler  wrote:
>
> On Thu, Oct 26, 2017 at 9:58 AM, Stefan Blumentrath
>  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
> ___
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> grass-user@lists.osgeo.org
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Re: [GRASS-user] Merging connected stream lines

[Markus Neteler]

On Thu, Oct 26, 2017 at 9:58 AM, Stefan Blumentrath
 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?

Markus
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Re: [GRASS-user] Merging connected stream lines

[Stefan Blumentrath]

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…

Cheers
Stefan

From: grass-user [mailto:grass-user-boun...@lists.osgeo.org] On Behalf Of 
Huidae Cho
Sent: torsdag 26. oktober 2017 09.07
To: GRASS user list 
Subject: [GRASS-user] Merging connected stream lines

Hi list!

I couldn't find an easy way to merge connected stream lines per network (stream 
output from r.watershed thinned and converted to vector). I'm not even sure if 
stream lines with tributaries can be merged into one feature. v.build.polylines 
merges multiple continuous lines, but it starts a new line at a confluence. If 
merging multiple lines with shared nodes is topologically impossible, what 
would be the best way to select all connected line features or assign the same 
category to those lines?

Any suggestions are welcome!

Thanks!
Huidae
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