[pgrouting-users] pgr_nodenetwork

[Toni Hérnández]

Maybe It would be a good idea to use the idiosyncrasy of the function 
St_Union() . St_Union merges all geometries of a table but it also 
re-structures the merged geometry in a way, that it is possible to 
obtain all the segments based on the intersection points of the previous 
geometries.

Using the test_graph table of the example we can obtain the 4 segments 
combining st_dump with st_union.

select (st_dump(st_union(geom))).geom from test_graph


*Toni Hernández Vallès*
Servei de Sistemes d'Informació Geogràfica i Teledetecció
-
Universitat de Girona
*SIGTE*
-
Pl. Ferrater Mora 1
17071 Girona
Tel +34 972 418 039 (7026 intern)
toni.hernandez at udg.edu <mailto:toni.hernandez at udg.edu>

http://www.sigte.udg.edu
Twitter http://twitter.com/SIGTE_UDG

El 16/03/2018 a les 04:24, Daniel Kastl ha escrit:
> Thank you for reporting the issue and the easy to reproduce test case!
>
> I tried with a different projection, but the issue remained.
> I think, it's better to track this in the pgRouting Github repository, 
> so I created the following issue: 
> https://github.com/pgRouting/pgrouting/issues/1009
>
> Best regards,
> Daniel
>
>
>
> On Fri, Mar 16, 2018 at 12:03 AM, Toni Hérnández 
> <toni.hernandez at udg.edu <mailto:toni.hernandez at udg.edu>> wrote:
>
>     Hello,
>
>     I have been trying to make some sense of the function
>     pgr_nodenetwork, but I haven't succeeded.
>
>     Based on the documentation, this function "Nodes an network edge
>     table.(...).  What we mean by “noded” is that at every
>     intersection in the road network all the edges will be broken into
>     separate road segments"
>
>     I have been doing tests for the last couple of days. You can
>     reproduce a simple one, by executing the following SQL statements.
>
>
>     -- Create test_graph table and insert two geometries
>
>     SET CLIENT_ENCODING TO UTF8;
>     SET STANDARD_CONFORMING_STRINGS TO ON;
>     BEGIN;
>     CREATE TABLE "test_graph" (gid serial,
>     "id" numeric(10,0),
>     "nom" varchar(80));
>     ALTER TABLE "test_graph" ADD PRIMARY KEY (gid);
>     SELECT
>     AddGeometryColumn('','test_graph','geom','25831','LINESTRING',2);
>     INSERT INTO "test_graph" ("id","nom",geom) VALUES
>     ('3',NULL,'0102000020E764000008000000F281433F6B731A41C84583B869855141592275DD14731A41C89C7A7D73855141B3E5D70CD3721A4164B5681680855141BFC2A67BBE721A419A3856BE8585514137F861B0A1721A41D72C1EC58F855141D87C445995721A413DC21EB6968551416D2458939D721A41DFF4EFE89D85514137F861B0A1721A411578DD90A3855141');
>     INSERT INTO "test_graph" ("id","nom",geom) VALUES
>     ('5',NULL,'0102000020E76400000900000065D6DA5A51701A410D5914A88B855141DA9E3C70E5701A4106E8394987855141ADE2BBDC85711A415E9B857C85855141C32F009B0D721A416B2643758485514150B2FF8D78721A41A8C313B784855141BFC2A67BBE721A419A3856BE85855141930626E85E731A4135FA4C92888551414E90077728741A418D04908A90855141A5E6108797741A41F399907B97855141');
>     COMMIT;
>     ANALYZE "test_graph";
>
>     -- Try to node the network.
>     select pgr_nodenetwork ('test_Graph', 0.01, 'gid', 'geom');
>
>
>     You can see the geometries on images, before
>     (http://sigserver4.udg.edu/apps/original_geometries.png
>     <http://sigserver4.udg.edu/apps/original_geometries.png>) and
>     after (http://sigserver4.udg.edu/apps/noded_geometries.png
>     <http://sigserver4.udg.edu/apps/noded_geometries.png>), the noding
>     proces.
>
>     The result, is a set of 6 rows but the segments generated are not
>     the expected ones.
>
>     Does anyone know what's happening here?
>
>     Thanks for your help.
>
>     -- 
>     *Toni Hernández Vallès*
>     Servei de Sistemes d'Informació Geogràfica i Teledetecció
>     -
>     Universitat de Girona
>     *SIGTE*
>     -
>     Pl. Ferrater Mora 1
>     17071 Girona
>     Tel +34 972 418 039 <tel:+34%20972%2041%2080%2039> (7026 intern)
>     toni.hernandez at udg.edu <mailto:toni.hernandez at udg.edu>
>
>     http://www.sigte.udg.edu
>     Twitter http://twitter.com/SIGTE_UDG
>
>
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>
>
> -- 
> Georepublic UG & Georepublic Japan
> eMail: daniel.kastl at georepublic.de <mailto:daniel.kastl at georepublic.de>
> Web: https://georepublic.info
>
>
>
>
>
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