[postgis-users] Corner coordinates from Geometry

[Paul Ramsey]

select st_x(st_centroid(geom)) as x, st_y(st_centroid(geom)) as y from mytable;

On Tue, Nov 24, 2009 at 9:46 AM, Robert Hicks <robhyx at gmail.com> wrote:
> Great thanks! I think either ST_PointOnSurface() or ST_Centroid()
> should be fine, but now I need convert the geometry string into
> latitude and longitude (Sorry, I should have been more clear before
> what I was ultimately looking for).
>
> On Tue, Nov 24, 2009 at 12:40 PM, Paul Ramsey <pramsey at cleverelephant.ca> wrote:
>> Ah, POINT(avg(X), avg(Y))...
>>
>> On Tue, Nov 24, 2009 at 9:38 AM, Kevin Neufeld <kneufeld at refractions.net> wrote:
>>> Maxime van Noppen wrote:
>>>>
>>>> Paul Ramsey wrote:
>>>>>
>>>>> Use ST_Centroid() then. It's just the mid-point of the bbox, so it's
>>>>> fast to calculate.
>>>>
>>>> It might be outside the polygon though.
>>>>
>>>
>>> In which case, if it matters, use ST_PointOnSurface().
>>>
>>> Paul, just a clarification, I believe centroid calculates the geometric
>>> centre of a geoemtry or "centre of mass" and not the mid-point of the bbox.
>>>  Here are a few pictorial examples:
>>> http://postgis.org/documentation/manual-1.5SVN/ST_Centroid.html
>>>
>>> -- Kevin
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