[postgis-users] The "bow tie" error

[Francois Hugues]

Hello,

I have to deal with a dataset with a lot of errors. I ran a st_makevalid which seems to give me good results (all polygons then appear to be valid, closed and simple). But, when I open this table as a layer in qgis it still throws me a lot of errors. The image attached to this message provide you with an example and the error said : Le segment 0 de l'anneau 16 du polygone 6 est intersecté au segment 0 de l'anneau 1 du polygone 7 à 933828.8196, 6261164.472 (in english this may be something like : line 0 of ring 16 is intersected by line 0 of ring 1 of polygon 7 at point...).

As the rings of the multipolygon share one point, I tried to dump it and then to union the rings to build a single polygon but I got a multipolygon back and still an error.

The dataset have a lot of "bow ties" and it seems that st_makevalid change them to multipolygon but that do not correct all errors in qgis.

Does anyone have an idea to find any solution ?

Hugues

--

 

Hugues FRANÇOIS 

hugues.francois at irstea.fr

-------------- next part --------------
A non-text attachment was scrubbed...
Name: qgis_error.jpg
Type: image/jpeg
Size: 47225 bytes
Desc: qgis_error.jpg
URL: <http://lists.osgeo.org/pipermail/postgis-users/attachments/20130321/d1ca6f25/attachment.jpg>