[postgis-users] newbie question about non closed rings

[Paragon Corporation]

Ge,

For this kind of thing I usually output to wkt and then use sed to convert
the POLYGON/MULTIPOLYGON to MULTILINESTRING format.  Then I bring the data
in as MULTILINESTRING/LINESTRING and use BuildArea to reform the POLYGONS
using the ST_SnapToGrid approach Kevin outlined.

I'm sure there is probably an easier way, but haven't thought of it.  Since
PostGIS won't allow these geometries in at all. 

Mark Cave-Ayland,
I forget were we planning on making this a switch option in later versions
of PostGIS?  So that you could bring in polygons with unclosed rings and fix
them in the db? 

Hope that helps,
Regina
-----Original Message-----
From: postgis-users-bounces at postgis.refractions.net
[mailto:postgis-users-bounces at postgis.refractions.net] On Behalf Of G. van
Es
Sent: Wednesday, April 15, 2009 1:44 PM
To: PostGIS Users Discussion
Subject: Re: [postgis-users] newbie question about non closed rings


Thanks for pointing me in this direction. 
Trying the following however doesn't give me the desired result.

select
st_isvalid(ST_SnapToGrid('01060000000100000001030000000100000017000000F16E09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',0.0001));

ERROR:  geometry contains non-closed rings



--- On Wed, 4/15/09, Kevin Neufeld <kneufeld at refractions.net> wrote:

> From: Kevin Neufeld <kneufeld at refractions.net>
> Subject: Re: [postgis-users] newbie question about non closed rings
> To: "PostGIS Users Discussion" <postgis-users at postgis.refractions.net>
> Date: Wednesday, April 15, 2009, 8:39 AM You could try snapping your 
> geometries to a grid after they are in the database.
> 
> http://postgis.refractions.net/documentation/manual-svn/ST_SnapToGrid.
> html
> 
> 
> postgis=# SELECT
> ST_IsValid('0106000000010000000103000000010000000700000024213D12AA7BFD
> 40945FF42576511941676A32F9017BFD40B1D67BEA7E511941C3E3C640DB7DFD4026CE
> 38F4EE531941C91289C5AA7EFD40017B8518E3531941646F1599AB7DFD409627F1F0AE
> 521941355EBA49547CFD407B14AEC74652194123213D12AA7BFD40945FF42576511941
> ');
> NOTICE:  IllegalArgumentException: points must form a closed 
> linestring  st_isvalid
> ------------
>  f
> (1 row)
> 
> 
> postgis=# SELECT
> ST_IsValid(ST_SnapToGrid('01060000000100000001030000000100000007000000
> 24213D12AA7BFD40945FF42576511941676A32F9017BFD40B1D67BEA7E511941C3E3C6
> 40DB7DFD4026CE38F4EE531941C91289C5AA7EFD40017B8518E3531941646F1599AB7D
> FD409627F1F0AE521941355EBA49547CFD407B14AEC74652194123213D12AA7BFD4094
> 5FF42576511941',
> 0.00001));
>  st_isvalid
> ------------
>  t
> (1 row)
> 
> 
> -- Kevin
> 
> G. van Es wrote:
> > The shapefile is created with software from Bentley.
> > PostgreSQL is version 8.3.4 on Ubuntu PostGis is version 1.3
> > 
> > I also see a difference between conversion as WKB and
> WKT (-w option). If I use shp2pgsql with the -w option there are far 
> less records that fail.
> > 
> > So can this be an issue with rounding up numbers? In
> WKT I see a tiny difference between some start and end points on 
> failing records.
> > 
> > And if so, is there a possibility to ignore those tiny
> differences?
> > 
> > Thanks again,
> > Ge
> > 
> > 
> _______________________________________________
> postgis-users mailing list
> postgis-users at postgis.refractions.net
> http://postgis.refractions.net/mailman/listinfo/postgis-users
> 


      
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