[postgis-users] Point inside a polygon

[Rémi Cura]

Oops my bad :-/

I use http://postgis.refractions.net/docs/ST_StartPoint.html for this kind
of stuff,

it is fast but the point may not be "within" enough for you
(http://en.wikipedia.org/wiki/DE-9IM)

Cheers,
Rémi-C


2014-05-05 17:10 GMT+02:00 <Steve.Toutant at inspq.qc.ca>:

> Having a centroid outside a polygon is a common situation, even with valid
> geometries.
>
> Depending of use case, I use ST_PointOnSurface when ST_Within(St_Centroid(surface),
> surface) returns false
>
> steve
>
>
>
>
>  *Rémi Cura <remi.cura at gmail.com <remi.cura at gmail.com>>@lists.osgeo.org
> <http://lists.osgeo.org>*
> Envoyé par : postgis-users-bounces at lists.osgeo.org
>
> 2014-05-05 07:09
>  Veuillez répondre à
> PostGIS Users Discussion <postgis-users at lists.osgeo.org>
>
>   A
> PostGIS Users Discussion <postgis-users at lists.osgeo.org>
> cc
>   Objet
> Re: [postgis-users] Point inside a polygon
>
>
>
>
>
>
> Hmm your problem is not about a function, is about using invalid
> geometries !
>
> Why simply don't fix your geometry?
> you must do it anyway if you want to use PostGIS
> without strange bugs.
>
> Use *http://postgis.refractions.net/docs/ST_MakeValid.html*<http://postgis.refractions.net/docs/ST_MakeValid.html>
>
> Cheers,
> Rémi-C
>
>
> 2014-05-03 15:51 GMT+02:00 Larry Reeder <*lnreeder at gmail.com*<lnreeder at gmail.com>
> >:
> Another thing to be aware of with ST_PointOnSurface is it can return a
> point that's on the boundary of polygon, but *not inside* the polygon, so
> that ST_Within(St_PointOnSurface(surface), surface) returns false.  That's
> bitten me before, but may be OK for your purposes.
>
>        -Larry
>
>
>
>
> On Fri, May 2, 2014 at 1:38 PM, Åsmund Tokheim <*asmundto at gmail.com*<asmundto at gmail.com>>
> wrote:
> Hi
>
> You can use st_closestpoint(geom, st_centroid(geom)) to make sure that the
> returned point is in most circumstances at or near the centroid, and always
> at least on the boundary of the polygon. While st_pointonsurface certainly
> will be faster, it will often choose a more random point on the surface.
>
> Åsmund
>
>
> On Fri, May 2, 2014 at 12:45 PM, Nicolas Ribot <*nicolas.ribot at gmail.com*<nicolas.ribot at gmail.com>>
> wrote:
> Hi,
>
> Use st_pointOnSurface (
> *http://postgis.net/docs/manual-2.1/ST_PointOnSurface.html*<http://postgis.net/docs/manual-2.1/ST_PointOnSurface.html>
> )
>
> Nicolas
>
>
> On 2 May 2014 06:32, J.Alejandro Martinez Linares <
> *islanis at infomed.sld.cu* <islanis at infomed.sld.cu>> wrote:
> Hi people, i need your help, i was using st_centroid to get a point that
> be inside a polygon butr st_centroid got a property  that is a problem to
> me, it returns a point that not always is inside the polygon, cause when
> the polygon has an irregular form, the point that st_centroid is outside
> the polygon, and i need a function that do a similar thing that st_centroid
> but i need that the point it returns always be inside the polygon, is there
> a function that do that?
>
> cheers.
>
> --
>
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