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<DIV dir=ltr align=left><FONT color=#0000ff size=2 face=Arial><SPAN
class=659415319-22062011>Sheara,</SPAN></FONT></DIV>
<DIV dir=ltr align=left><FONT color=#0000ff size=2 face=Arial><SPAN
class=659415319-22062011></SPAN></FONT> </DIV>
<DIV dir=ltr align=left><FONT color=#0000ff size=2 face=Arial><SPAN
class=659415319-22062011>Here is a function we use that seems to work pretty
well for our use-case.</SPAN></FONT></DIV>
<DIV dir=ltr align=left><FONT color=#0000ff size=2 face=Arial><SPAN
class=659415319-22062011></SPAN></FONT> </DIV>
<DIV dir=ltr align=left><FONT color=#0000ff size=2 face=Arial><SPAN
class=659415319-22062011>CREATE OR REPLACE FUNCTION
point_inside_geometry(param_geom geometry)<BR> RETURNS geometry
AS<BR>$$<BR> DECLARE <BR> var_cent geometry :=
ST_Centroid(param_geom); <BR> var_result geometry :=
var_cent;<BR> BEGIN<BR> -- If the centroid is outside the geometry
then <BR> -- calculate a box around centroid that is guaranteed to
intersect the geometry<BR> -- take the intersection of that and find point
on surface of intersection<BR> IF NOT ST_Intersects(param_geom, var_cent)
THEN<BR> var_result := ST_PointOnSurface(ST_Intersection(param_geom,
ST_Expand(var_cent, ST_Distance(var_cent,param_geom)*2) ));<BR> END
IF;<BR> RETURN var_result;<BR> END;<BR> $$<BR> LANGUAGE
plpgsql IMMUTABLE STRICT<BR> COST 100;</SPAN></FONT></DIV>
<DIV> </DIV>
<DIV><SPAN class=659415319-22062011></SPAN><FONT color=#0000ff size=2
face=Arial><SPAN class=659415319-22062011>Regina and Leo</SPAN></FONT></DIV>
<DIV><SPAN class=659415319-22062011></SPAN><SPAN
class=659415319-22062011></SPAN><FONT face=Arial><FONT color=#0000ff><FONT
size=2><A href="http://www.postgis.us">h<SPAN
class=659415319-22062011>ttp://www.postgis.us</A></SPAN></FONT></FONT></FONT><BR></DIV>
<DIV dir=ltr lang=en-us class=OutlookMessageHeader align=left>
<HR tabIndex=-1>
<FONT size=2 face=Tahoma><B>From:</B>
postgis-users-bounces@postgis.refractions.net
[mailto:postgis-users-bounces@postgis.refractions.net] <B>On Behalf Of
</B>Sheara Cohen<BR><B>Sent:</B> Wednesday, June 22, 2011 3:19 PM<BR><B>To:</B>
postgis-users@postgis.refractions.net<BR><B>Subject:</B> [postgis-users]
Centroid 'Within'<BR></FONT><BR></DIV>
<DIV></DIV>
<DIV class=WordSection1>
<P class=MsoNormal>Hi All – I’m wondering if anyone has figured out a solution
to converting a polygon file to a centroid point file that produces centroids
within the polygons. Obviously, ST_Centroid doesn’t produce centroids within the
polygon. And ST_PointOnSurface produces a point within that is only sort of
centroid-ish…<o:p></o:p></P>
<P class=MsoNormal><o:p> </o:p></P>
<P class=MsoNormal>Any ideas would be great. Thank you!<o:p></o:p></P>
<P class=MsoNormal><o:p> </o:p></P>
<P class=MsoNormal>~ Sheara<o:p></o:p></P>
<P class=MsoNormal><o:p> </o:p></P>
<P class=MsoNormal><B><SPAN
style="FONT-FAMILY: 'Century Gothic','sans-serif'; LETTER-SPACING: 1pt; COLOR: gray; FONT-SIZE: 10pt">Sheara
Cohen</SPAN></B><SPAN
style="FONT-FAMILY: 'Century Gothic','sans-serif'; FONT-SIZE: 9pt"><BR></SPAN><SPAN
style="FONT-VARIANT: small-caps; FONT-FAMILY: 'Century Gothic','sans-serif'; LETTER-SPACING: 1.4pt; COLOR: gray; FONT-SIZE: 7.5pt">Planner</SPAN><SPAN
style="LETTER-SPACING: 1pt"><o:p></o:p></SPAN></P>
<P style="mso-margin-top-alt: auto; mso-margin-bottom-alt: auto"
class=MsoNormal><B><SPAN
style="FONT-FAMILY: 'Century Gothic','sans-serif'; COLOR: #e9935f; FONT-SIZE: 10pt">C
A L T H O R P E</SPAN></B><B><SPAN
style="FONT-FAMILY: 'Century Gothic','sans-serif'; COLOR: gray; FONT-SIZE: 10pt"> A
S S O C I A T E S</SPAN></B><SPAN
style="FONT-FAMILY: 'Century Gothic','sans-serif'; COLOR: gray; FONT-SIZE: 10pt"><BR></SPAN><SPAN
style="FONT-FAMILY: 'Century Gothic','sans-serif'; COLOR: gray; FONT-SIZE: 7.5pt">2095
ROSE STREET, SUITE 201, BERKELEY, CALIFORNIA, 94709 USA</SPAN><SPAN
style="FONT-FAMILY: 'Century Gothic','sans-serif'; FONT-SIZE: 8pt"><BR><BR></SPAN><SPAN
style="FONT-FAMILY: 'Century Gothic','sans-serif'; COLOR: gray; FONT-SIZE: 7.5pt"><o:p></o:p></SPAN></P>
<P class=MsoNormal><o:p> </o:p></P></DIV></BODY></HTML>