[postgis-users] The "bow tie" error

[Stephen Woodbridge]

On 3/21/2013 5:06 PM, Stephen Woodbridge wrote:
> Francois,
>
> Can you dump the polygons in the multiplyogon and create separate
> records for them. So in you example graphic, you would end up with two
> separate polygons the touch at a point. I think this would be OK for qgis.

This might be helpful:

http://www.bostongis.com/postgis_dump.snippet
http://postgis.17.n6.nabble.com/converting-multipolygon-to-polygon-td3530291.html

> -Steve W
>
> On 3/21/2013 4:57 PM, Francois Hugues wrote:
>> 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
>>
>>
>>
>> _______________________________________________ postgis-users mailing
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>
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