Re: [postgis-users] Build topology for polygon layer using postgis2.0
On Sun, Oct 30, 2011 at 10:37:31PM -0700, Elton Chan wrote:
> Hi there,
>
> I would like to build topology for a polygon layer using postgis 2.0. The
> polygon layer contains contiguous polygons snap to each another but some are
> having some geometry error such as gap is found between polygons.
>
> Does anybody know the procedure to build topology with abovemention polygon
> data? More precisely, any procedure to convert all the polygons to line
> strings, then remove duplicate lines, and build topology and remove
> small polygons.
SELECT topology.CreateTopology('test', 4326);
SELECT topology.ST_CreateTopoGeo(ST_Collect(the_geom)) from mylayer;
Let it go while trick & treating as it'll take a lot...
A more scalable solution (the above does most work in memory) and one
which would also create the TopoGeometry objects for you to re-construct
the original point set in a value to use in your table, is the toTopoGeometry
function which takes a GEOMETRY and put it into a topology giving you back
the topologically-defined version of your GEOMETRY. Such function is yet
to be done but is planned: http://trac.osgeo.org/postgis/ticket/1017
and it is looking for co-funders (let me know if you're interested).
--strk;
() Free GIS & Flash consultant/developer
/\ http://strk.keybit.net/services.html
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[postgis-users] Build topology for polygon layer using postgis2.0
Hi there, I would like to build topology for a polygon layer using postgis 2.0. The polygon layer contains contiguous polygons snap to each another but some are having some geometry error such as gap is found between polygons. Does anybody know the procedure to build topology with abovemention polygon data? More precisely, any procedure to convert all the polygons to line strings, then remove duplicate lines, and build topology and remove small polygons. Thanks, elton ___ postgis-users mailing list postgis-users@postgis.refractions.net http://postgis.refractions.net/mailman/listinfo/postgis-users
Re: [postgis-users] no row selected on spatial query
Puneet - I think this can happen if you load a shapefile that is projected into a table specifying a lat long srid. I don't think the definition restricts the range of units. You will have to change the column definition I guess. cheers Ben On 28/10/2011, at 8:06 AM, Puneet Kishor wrote: > A brief follow-up on this -- > > On Oct 27, 2011, at 5:57 PM, Puneet Kishor wrote: > >> I inherited two tables like so >> >> db=# select ST_Extent(the_geom) from t1; >> st_extent >> - >> BOX(-180 5.67656603969958,180 89.951703269) >> (1 row) >> >> db=# select ST_Extent(the_geom) from t2; >> st_extent >> --- >> BOX(-3666182.8927 1296299.9824,4440422.8742 8820425.3008) >> (1 row) >> >> I want to convert t2 to match t1. So, I tried the following -- >> >> db=# UPDATE t2 SET the_geom = ST_Transform(the_geom, 4326); >> UPDATE 1354 >> >> >> But that didn't do it. >> >> db=# select ST_Extent(the_geom) from t2; >> st_extent >> --- >> BOX(-3666182.8927 1296299.9824,4440422.8742 8820425.3008) >> (1 row) >> >> >> What do I do to transform t2 so its geometry matches t1? >> > > Turns out t2 was loaded from a shapefile using shp2pgsql using SRID 4326. Its > table definition is like so > > CREATE TABLE t2 > ( > gid serial NOT NULL, > objectid integer, > type integer, > the_geom geometry, > CONSTRAINT t2_pkey PRIMARY KEY (gid ), > CONSTRAINT enforce_dims_the_geom CHECK (st_ndims(the_geom) = 2), > CONSTRAINT enforce_geotype_the_geom CHECK (geometrytype(the_geom) = > 'POINT'::text OR the_geom IS NULL), > CONSTRAINT enforce_srid_the_geom CHECK (st_srid(the_geom) = 4326) > ) > WITH ( > OIDS=FALSE > ); > > So, in spite of the `enforce_srid_the_geom` CONSTRAINT which should restrict > geometry to 4326, seems like meter values got inserted into the table. How is > that possible? > > And, in any case, how can I repair this? > > -- > Puneet Kishor > > ___ > postgis-users mailing list > postgis-users@postgis.refractions.net > http://postgis.refractions.net/mailman/listinfo/postgis-users ___ postgis-users mailing list postgis-users@postgis.refractions.net http://postgis.refractions.net/mailman/listinfo/postgis-users
