[Qgis-developer] Valid or invalid geom in PostGIS?
Mark Johnson
mj10777 at googlemail.com
Mon Jan 16 04:23:43 PST 2017
This is a GEOS error that is being reported
- your Geometry has a Topological error
> 2017-01-16T11:34:52 1 NOTA: NOTICE: Self-intersection at or near
> point
> > 619746.32941695023 4869530.4882389866
> > 2017-01-16T11:34:52 1 NOTA: NOTICE: IllegalArgumentException:
> Invalid
> > number of points in LinearRing found 3 - must be 0 or >= 4
Look for 'ST_SelfIntersections(..)' in PostGis
- it will show the points that cause such errors
-- not sure of PostGis has this command
The first error
- is often a POLYGON that has been created from single LINESTRINGs
-- 1 or more of these LINESTRINGs have been included more than once
--- remove the double LINESTRINGs to correct
---> will start at the given point: 619746.32941695023 4869530.4882389866
The error message will only show the first POINT, if there are more than
one you should look for the next.
The second error means that the ExteriorRing of the POLYGON only has 3
POINTs
- 4 are required to be Topologicaly correct
SELECT ST_NumPoints(ST_ExteriorRing(geometry))
- should return 3 in this case, but should be 4 at least
Certain functions, that use GEOS, will not bring correct results
- when Topological error exists
-- and should be corrected
Mark Johnson
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