[postgis-users] How is Centroid(Geometry) calculated?

[Matt Doughty]

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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