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<font face="Arial">thanks Hugues,<br>
<br>
The thing is that with st_Dump I get all the linestrings of a
river but there is no way (that I know of) that I can order all
the segments and get the "real" start /end points of the whole
river.<br>
<br>
</font>
<div class="moz-signature"><span style="font-size:8.5pt">
<b>Toni Hernández Vallès</b>
<br>
Servei de Sistemes d'Informació Geogràfica i Teledetecció<br>
-<br>
Universitat de Girona<br>
<b>SIGTE</b><br>
-<br>
Pl. Ferrater Mora 1<br>
17071 Girona<br>
Tel +34 972 418 039 (7026 intern)<br>
<a href="mailto:toni@sigte.udg.edu">toni@sigte.udg.edu</a>
<br>
<br>
<a href="http://www.sigte.udg.edu">http://www.sigte.udg.edu</a><br>
Twitter <a href="http://twitter.com/SIGTE_UDG">http://twitter.com/SIGTE_UDG</a><br>
<br>
</span></div>
<div class="moz-cite-prefix">On 09/06/2015 08:56, Hugues François
wrote:<br>
</div>
<blockquote
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<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"
lang="EN-GB">Hello,<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"
lang="EN-GB"><o:p> </o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"
lang="EN-GB">I think ST_Dump could help to deal with
multilinestrings: <a moz-do-not-send="true"
href="http://postgis.net/docs/ST_Dump.html">http://postgis.net/docs/ST_Dump.html</a><o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"
lang="EN-GB"><o:p> </o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"
lang="EN-GB">Hugues.<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"
lang="EN-GB"><o:p> </o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"
lang="EN-GB"><o:p> </o:p></span></p>
<div>
<div style="border:none;border-top:solid #B5C4DF
1.0pt;padding:3.0pt 0cm 0cm 0cm">
<p class="MsoNormal"><b><span
style="font-size:10.0pt;font-family:"Tahoma","sans-serif";color:windowtext">De :</span></b><span
style="font-size:10.0pt;font-family:"Tahoma","sans-serif";color:windowtext">
<a class="moz-txt-link-abbreviated" href="mailto:postgis-users-bounces@lists.osgeo.org">postgis-users-bounces@lists.osgeo.org</a>
[<a class="moz-txt-link-freetext" href="mailto:postgis-users-bounces@lists.osgeo.org">mailto:postgis-users-bounces@lists.osgeo.org</a>] <b>De la
part de</b> toni hernández<br>
<b>Envoyé :</b> mardi 9 juin 2015 08:09<br>
<b>À :</b> <a class="moz-txt-link-abbreviated" href="mailto:postgis-users@lists.osgeo.org">postgis-users@lists.osgeo.org</a><br>
<b>Objet :</b> Re: [postgis-users] Get only the main
river. Smoothline???<o:p></o:p></span></p>
</div>
</div>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal" style="margin-bottom:12.0pt"><span
style="font-family:"Arial","sans-serif"">Thanks
Remi,<br>
<br>
I thought that but I have no starting/ending points.
St_StartPoint and St_EndPoint are not working with
MultiLinestrings<br>
I'll give it some more intense thought. :)<br>
<br>
Cheers.</span><o:p></o:p></p>
<div>
<p class="MsoNormal" style="margin-bottom:12.0pt"><b><span
style="font-size:8.5pt">Toni Hernández Vallès</span></b><span
style="font-size:8.5pt"> <br>
Servei de Sistemes d'Informació Geogràfica i Teledetecció<br>
-<br>
Universitat de Girona<br>
<b>SIGTE</b><br>
-<br>
Pl. Ferrater Mora 1<br>
17071 Girona<br>
Tel +34 972 418 039 (7026 intern)<br>
<a moz-do-not-send="true" href="mailto:toni@sigte.udg.edu">toni@sigte.udg.edu</a>
<br>
<br>
<a moz-do-not-send="true" href="http://www.sigte.udg.edu">http://www.sigte.udg.edu</a><br>
Twitter <a moz-do-not-send="true"
href="http://twitter.com/SIGTE_UDG">http://twitter.com/SIGTE_UDG</a></span><o:p></o:p></p>
</div>
<div>
<p class="MsoNormal">On 08/06/2015 17:45, Rémi Cura wrote:<o:p></o:p></p>
</div>
<blockquote style="margin-top:5.0pt;margin-bottom:5.0pt">
<div>
<div>
<p class="MsoNormal" style="margin-bottom:12.0pt"><span
style="font-family:"Courier New"">if you
have start and end point of geom B,<br>
you can get the river path with a shortest path method
(one liner using python, can be done in few hours
using plpgsql).<o:p></o:p></span></p>
</div>
<div>
<p class="MsoNormal"><span
style="font-family:"Courier New"">The idea
is that you cut your geom into segments(pairs of
points)<br>
, the length of the segment is the weight of this edge
<br>
, and you know which segment is connected to which
segment (adjacency graph).<o:p></o:p></span></p>
</div>
<div>
<p class="MsoNormal"><span
style="font-family:"Courier New"">Then you
use <a moz-do-not-send="true"
href="http://networkx.lanl.gov/reference/generated/networkx.algorithms.shortest_paths.generic.shortest_path.html#networkx.algorithms.shortest_paths.generic.shortest_path">Networkx
</a>shortest path distance.<o:p></o:p></span></p>
</div>
<div>
<p class="MsoNormal"><span
style="font-family:"Courier New""><br>
Else, <o:p></o:p></span></p>
</div>
<div>
<p class="MsoNormal"><span
style="font-family:"Courier New"">you are up
to use some nasty workaround I suppose (playing with
buffers on your original river surface, testing which
segment intersects etc. ).<o:p></o:p></span></p>
</div>
<div>
<p class="MsoNormal" style="margin-bottom:12.0pt"><span
style="font-family:"Courier New"">I tried
that but it ends up being more work (and more corner
cases) than doing the things properly (in my
experience).<o:p></o:p></span></p>
</div>
<div>
<p class="MsoNormal"><span
style="font-family:"Courier New"">Cheers,<o:p></o:p></span></p>
</div>
<div>
<p class="MsoNormal"><span
style="font-family:"Courier New"">Rémi-C<o:p></o:p></span></p>
</div>
</div>
<div>
<p class="MsoNormal"><o:p> </o:p></p>
<div>
<p class="MsoNormal">2015-06-08 16:42 GMT+02:00 toni
hernández <<a moz-do-not-send="true"
href="mailto:toni@sigte.udg.edu" target="_blank">toni@sigte.udg.edu</a>>:<o:p></o:p></p>
<div>
<p class="MsoNormal" style="margin-bottom:12.0pt"><span
style="font-family:"Arial","sans-serif"">Hi
everyone,<br>
<br>
I have a multilinestring with a river and all its
afluents as you can see in this image <br>
<a moz-do-not-send="true"
href="http://sigserver4.udg.edu/apps/geometries.png"
target="_blank">http://sigserver4.udg.edu/apps/geometries.png</a><br>
<br>
I got geometry A using St_StraithSkeleton.<br>
<br>
Is there a way to go from geometry A to geometry B??
<br>
Maybe something similar to SmoothLine???<br>
<br>
</span><o:p></o:p></p>
<div>
<p class="MsoNormal" style="margin-bottom:12.0pt">-- <br>
<b><span style="font-size:8.5pt">Toni Hernández
Vallès</span></b><span style="font-size:8.5pt">
<br>
Servei de Sistemes d'Informació Geogràfica i
Teledetecció<br>
-<br>
Universitat de Girona<br>
<b>SIGTE</b><br>
-<br>
Pl. Ferrater Mora 1<br>
17071 Girona<br>
Tel +34 972 418 039 (7026 intern)<br>
<a moz-do-not-send="true"
href="mailto:toni@sigte.udg.edu" target="_blank">toni@sigte.udg.edu</a>
<br>
<br>
<a moz-do-not-send="true"
href="http://www.sigte.udg.edu" target="_blank">http://www.sigte.udg.edu</a><br>
Twitter <a moz-do-not-send="true"
href="http://twitter.com/SIGTE_UDG"
target="_blank">http://twitter.com/SIGTE_UDG</a></span><o:p></o:p></p>
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