[postgis-users] postgis topology

[Rémi Cura]

You can use ST_IsValid() to know if it is "valid" for postgres.
Even best, you can try to see what it looks like in qgis.

Cheers,
Rémi-C


2014/1/15 Ludovic Granjon <ludovic.granjon at u-bourgogne.fr>

>  Hello
>
> I think, I can do
> SELECT st_geometryN(geom,1) FROM ec;
> without error
>
> I get
>
> "POLYGON((504935.641400002 2310827.805,504952.193899997
> 2310825.6349,504964.4124 2310824.033,504964.191799998
> 2310823.56,504964.037199996 2310822.9832,504963.987400003
> 2310822.5117,504948.949900001 2310822.7941,504940.407399997
> 2310823.3589,504932.090300001 2310824.5769,504931.797399998
> 2310824.7718,504931.360100001 2310824.9757,504930.894100003
> 2310825.1006,504930.735399999 2310825.1239,504929.7368
> 2310825.2555,504929.7368 2310825.8138,504929.847599998
> 2310828.5646,504935.641400002 2310827.805))"
>
> Thanks
>
> Ludovic
>
>
>
> Le 15/01/2014 10:47, Christophe Vergon a écrit :
>
> Hello,
>
> Is st_geometryN(r.geomp,1)  a valid geometry ?
>
>
>
> Ludovic Granjon a écrit :
>
> Hello (Bonjour Christophe)
>
> I don't use french cadastre, only specific archaelogical data.
>
> Thanks for this, I try but, I don't realy understand how worked
> topogeo_addpolygon.
> If I do :
>
> CREATE EXTENSION postgis;
> CREATE EXTENSION postgis_topology;
> SET search_path = topology,public;
>
> I import my layer with QGIS
>
> SELECT topology.CreateTopology('ec_topo', 27572);
> SELECT
> topology.AddTopoGeometryColumn('ec_topo','public','ec','topo_geom','POLYGON');
>
> DO $$DECLARE r record;
> BEGIN
>   FOR r IN SELECT * FROM ec LOOP
>     BEGIN
>     SELECT topology.TopoGeo_AddPolygon('ec_topo',st_geometryn(r.geom,1),1);
>     EXCEPTION
>       WHEN OTHERS THEN
>         RAISE WARNING 'Loading of record % failed: %', r.id, SQLERRM;
>     END;
>   END LOOP;
> END$$;
>
> I have :
> ATTENTION:  Loading of record 1 failed: la requête n'a pas de destination
> pour les données résultantes
>
> I don't know where I'm wrong
>
> If you have an idea
>
> Thanks
>
> Regards
>
> Ludovic
>
> PS : (si j'avais sur que c'était toi qui répondrait, j'aurai écrit sur nos
> forums francophone ;-) )
>
> Le 15/01/2014 08:25, Christophe Vergon a écrit :
>
> Hello, (bonjour)
>
> When you udpdate a topology by using a SET statement if a polygon
> intersect an other you will have this error.
> If you want to create a topology from polygons try to use the
> topogeo_addpolygon function, the intersection between two polygons will be
> a new face.
>
> If, as I mean, you use a french survey "cadastre" data set, it's the best
> way to do that.
>
>
>
> Ludovic Granjon a écrit :
>
> Hi all
>
> I try to import a polygon layer to postgis and build topology with
> tolerance.
> I try something like that
>
> SELECT CreateTopology('ec_topo2', 27572);
> SELECT AddTopoGeometryColumn('ec_topo2', 'public', 'ec', 'topogeom2',
> 'MULTIPOLYGON');
> UPDATE ec SET topogeom2 = toTopoGeom(geom, 'ec_topo', 1, 1.0);
>
> But when I do that, I have
>
> ********** Erreur **********
>
> ERREUR: Spatial exception - geometry intersects edge 262
> État SQL :P0001
> Contexte : fonction PL/pgsql « topogeo_addlinestring », ligne 124 à
> affectation
> SQL statement "SELECT array_cat(edges, array_agg(x)) FROM ( select
> topology.TopoGeo_addLinestring(atopology, rec.geom, tol) as x ) as foo"
> fonction PL/pgsql « topogeo_addpolygon », ligne 24 à affectation
> fonction PL/pgsql « totopogeom », ligne 112 à FOR sur des lignes de SELECT
> fonction PL/pgsql « totopogeom », ligne 94 à affectation
>
> I try to modify the tolerance parameter but it still doesn't work
>
> Have  you a solution for that ?
>
> Thanks a lot
>
> Regards
>
> Ludovic
>
>
>
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