[postgis-users] Center of Points

[Gustavo Henrique Sberze Ribas]

Hello,

> Select 
> AsText(Centroid(geomcollfromtext('GEOMETRYCOLLECTION(POINT(.. 
> ..),POINT( .. ..),..)',4326)))
>
> and i got back POINT(nan nan);
>
> How can I get the center of many points?


  This seems to be the correct approach, however I'd transform the
coordinates to UTM before attempting any cartesian calculation.
What version of postgis are you using? The following example works 
fine for me. In the picture, the polygon depicts the convex hull
of the geometry collection and the black dot is the centroid.

select asText(centroid(geomCollFromText('
  GEOMETRYCOLLECTION (
POINT(-47.2412222222222 -22.7405833333333)
POINT(-47.3199166666667 -22.7333333333333)
POINT(-47.3545555555556 -22.7443055555556)
POINT(-47.3008346557617 -22.7133331298828)
POINT(-47.3302764892578 -22.731388092041)
POINT(-47.3406111111111 -22.76525)
POINT(-47.29525 -22.7161388888889)
POINT(-47.3481666666667 -22.7247222222222)
POINT(-47.3160277777778 -22.7383888888889)
POINT(-47.3275 -22.7459722222222)
POINT(-47.34025 -22.7523333333333)
POINT(-47.3368988037109 -22.7385997772217)
POINT(-47.3527793884277 -22.7352771759033)
POINT(-47.3476388888889 -22.7324444444444)
POINT(-47.3481666666667 -22.7247222222222)
POINT(-47.2624722222222 -22.7496944444444)
POINT(-47.34025 -22.7523333333333)
POINT(-47.3160277777778 -22.7383888888889)
POINT(-47.3406111111111 -22.76525)
POINT(-47.3275 -22.7459722222222)
POINT(-47.3001944444444 -22.7144444444444)
POINT(-47.3520555555556 -22.7320277777778)
POINT(-47.2952222222222 -22.7311111111111)
POINT(-47.3071944444444 -22.7513888888889)
POINT(-47.2978611111111 -22.7079722222222)
POINT(-47.3025833333333 -22.7260555555556)
POINT(-47.3317777777778 -22.7485)
POINT(-47.2861111111111 -22.7694444444444)
POINT(-47.2861111111111 -22.7722222222222)
POINT(-47.2944444444444 -22.775)
POINT(-47.2861111111111 -22.7805555555556)
POINT(-47.5083333333333 -22.5055555555556))',4326)))

--
Gustavo

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