[postgis-users] Method to remove overlaps in a layer

[Sandro Santilli]

So as of r9630 this topology of yours builds.
Of course your input geometries are not going to being fully
represented as the tolerance of 10 units on the topology is
chewing them badly.

Use tolerance with care !

Let me know how your next topos go :)

--strk;

  ,------o-. 
  |   __/  |    Delivering high quality PostGIS 2.0 !
  |  / 2.0 |    http://strk.keybit.net - http://vizzuality.com
  `-o------'


On Wed, Apr 11, 2012 at 02:53:07PM -0400, Pierre Racine wrote:
> An even simpler example leads to another type of error:
> 
> SELECT CreateTopology('topo3',0, 10);
> 
> DROP TABLE IF EXISTS ovlp.test03;
> CREATE TABLE ovlp.test03 AS
> SELECT 1 id, ST_GeomFromText('POLYGON((0 1, 2 2, 2 0, 0 1))') geom
> UNION ALL
> SELECT 2 id, ST_GeomFromText('POLYGON((1 1, 3 2, 3 0, 1 1))') geom
> 
> CREATE TABLE ovlp.test03_topo (id integer);
> 
> SELECT AddTopoGeometryColumn('topo3', 'ovlp', 'test03_topo', 'topo', 'POLYGON'); -- 1
> 
> INSERT INTO ovlp.test03_topo (id, topo)
> SELECT id, topology.toTopoGeom(geom, 'topo3', 1)
> FROM ovlp.test03
> 
> gives:
> 
> ********** Error **********
> 
> ERROR: SQL/MM Spatial exception - edge crosses node.
> SQL state: P0001
> Context: PL/pgSQL function "topogeo_addpoint" line 96 at assignment
> PL/pgSQL function "topogeo_addlinestring" line 125 at assignment
> SQL statement "SELECT array_cat(edges, array_agg(x)) FROM ( select topology.TopoGeo_addLinestring(atopology, rec.geom, tol) as x ) as foo"
> PL/pgSQL function "topogeo_addpolygon" line 27 at assignment
> SQL statement "INSERT INTO topo3.relation(topogeo_id, layer_id, element_type, element_id) SELECT 2, 1, 3, topogeo_addPolygon('topo3', '01030000000100000004000000000000000000F03F000000000000F03F0000000000000840000000000000004000000000000008400000000000000000000000000000F03F000000000000F03F'::geometry, 10);"
> PL/pgSQL function "totopogeom" line 129 at EXECUTE statement
> 
> Pierre
> 
> > -----Original Message-----
> > From: postgis-users-bounces at postgis.refractions.net [mailto:postgis-users-
> > bounces at postgis.refractions.net] On Behalf Of Pierre Racine
> > Sent: Wednesday, April 11, 2012 2:40 PM
> > To: PostGIS Users Discussion
> > Subject: Re: [postgis-users] Method to remove overlaps in a layer
> > 
> > So I have been creating a very simple example based on the example in the
> > toTopoGeom() documentation page:
> > 
> > http://www.postgis.org/documentation/manual-svn/toTopoGeom.html
> > 
> > SELECT CreateTopology('topo1',31467, 10);
> > 
> > CREATE TABLE ovlp.test02_topo (id integer);
> > 
> > SELECT AddTopoGeometryColumn('topo1', 'ovlp', 'test02_topo', 'topo',
> > 'POLYGON');
> > 
> > INSERT INTO ovlp.test02_topo (id, topo)
> > SELECT id, topology.toTopoGeom(geom, 'topo1', 1)
> > FROM ovlp.test02
> > 
> > And I get:
> > 
> > ********** Error **********
> > 
> > ERROR: interpolate_point4d: invalid F (1)
> > SQL state: XX000
> > Context: PL/pgSQL function "st_modedgesplit" line 94 at assignment
> > PL/pgSQL function "topogeo_addpoint" line 91 at assignment
> > PL/pgSQL function "topogeo_addlinestring" line 132 at assignment
> > SQL statement "SELECT array_cat(edges, array_agg(x)) FROM ( select
> > topology.TopoGeo_addLinestring(atopology, rec.geom, tol) as x ) as foo"
> > PL/pgSQL function "topogeo_addpolygon" line 27 at assignment
> > SQL statement "INSERT INTO topo1.relation(topogeo_id, layer_id,
> > element_type, element_id) SELECT 5, 1, 3, topogeo_addPolygon('topo1',
> > '0103000020EB7A0000010000000800000000000080FD384B4100000000F46154
> > 4100000000D84B4B41000000405069544100000000B55D4B41000000005C6354
> > 4100000000BD594B4100000000965B544100000000C8694B4100000000625554
> > 4100000080E15C4B4100000080474D544100000080ED404B41000000006C5054
> > 4100000080FD384B4100000000F4615441'::geometry, 10);"
> > PL/pgSQL function "totopogeom" line 129 at EXECUTE statement
> > 
> > I join a picture of the original layer to be converted to a topologic layer.
> > 
> > I'm still at beta 5... Should upgrading solve that particular problem?
> > 
> > Pierre
> > 
> > > > So what would be the normal/easiest steps to convert a messy polygon
> > > coverage into a clean topology? Is it documented somewhere?
> > > >
> > > > My guess:
> > > >
> > > > 1- SET search_path TO topology,public;
> > >
> > > You shouldn't need this, when you load topology.sql you should
> > > get "topology" already appended to the end of the search_path
> > > associated with the database.
> > >
> > > > 2- SELECT CreateTopoGeom('test')
> > >
> > > Yep.
> > >
> > > > 3- SELECT toTopoGeom(geom, 'test', 1)
> > > > FROM mymessyone;
> > >
> > > You didn't create a layer, see AddTopoGeometryColumn.
> > > The third argument is a layer id, as returned by that function.
> > >
> > > > or
> > > >
> > > > SELECT ST_CreateTopoGeo('test', geom)
> > > > FROM mymessyone;
> > >
> > > This one only works starting with an empty topology so
> > > you'll need to pass it a full collection:
> > >
> > > SELECT ST_CreateTopoGeo('test', ST_Collect(geom)) FROM mymessyone;
> > >
> > > But I'd recommend using toTopoGeom instead, to keep the linking
> > > between attributes and geometries.
> > >
> > > > What happens when a polygon to be added to the topology overlaps a
> > > polygon already in the topology?
> > >
> > > Two overlapping rectangles would produce a total of 3 faces.
> > > If you're returning TopoGeometry objects (your step 2) both
> > > of them will be defined by 2 faces, having one face in common.
> > 
> 
> _______________________________________________
> postgis-users mailing list
> postgis-users at postgis.refractions.net
> http://postgis.refractions.net/mailman/listinfo/postgis-users