Hi Matt,
It you want a point always inside your geometries use pointonsurface()
instead.
The centroid is not always on the geometries
it deals with the "convexity/concavity" of your geometries
Matt Doughty a écrit :
Hi,
Can anybody explain how PostGIS calculates centroids? I’ve checked the
manual but the relevant section doesn’t refer to an OGC Specification.
From what I can understand, it takes an average of the coordinates of
all the vertices of an entry, ignoring whether or not the centroid
falls outside the polygons. Is this right? This differs from other
GIS- GeoMedia, for example, when confronted with a multipolygon entry,
always puts the centroid inside the largest polygon.
Can anybody shed some light on this?
Cheers,
Matt
Matt Doughty
GEOGRAMA S.L.
Tel.: +34 945 13 13 72 652 77 14 15
Fax: +34 945 23 03 40
www.geograma.com
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