[postgis-users] Topology Postgis 2.0

Sandro Santilli strk at keybit.net
Thu Sep 27 05:50:29 PDT 2012

On Thu, Sep 27, 2012 at 02:44:12PM +0200, Sandro Santilli wrote:
> On Thu, Sep 27, 2012 at 04:58:24AM -0700, ps.tiara wrote:

> > but when i visualized the result of topology in x3d, it was mess..maybe i
> > made a mistake by wrong query??
> How did you visualize ? What do you mean by "messy" ?
> The topology in your backup results valid, and I can see it just fine.
> But yes, I do see a lot of very small faces, a lot of edges close 
> to one other.

One more tip, you can "see" how many "messy" faces you have with this

with inp as (
 SELECT face_id, st_area(ST_GetFaceGeometry('simpanglima_topo', face_id))
 FROM simpanglima_topo.face where face_id > 0
) SELECT * from inp order by st_area;

You'll see there are only 4 faces with an area > 10 square units, while
92 faces have an area < 0.0000006 square units...

It's still topologically valid, but probably not what you want.
It'd be an interesting research topic (since you're doing a research)
to figure out HOW to fix that situation _now_ that you have it encoded
as a topology. 

I think you'll basically want to delete each face and make it part
of one of the big ones. You could recursively find an edge shared
between a big face and a small face and remove it.


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