[postgis-users] Centroid Within Multi Part Polygon

[Obe, Regina]

Simon,
 
I must commend you on the very nice instructive site you have.  Now for a nit-pcik.  Your link to the PostGIS site is broken!
 
This might be a stupid question - but it wasn't obvious to me so I will ask it.
 
I presume the function you have is embedded in your
 
http://www.spatialdbadvisor.com/files/spatialdbadvisor_oracle_spatial_types_and_packages.zip
 
But wasn't quite clear what it would be named and what .sql file to find it in or if it depends on numerous files.
 
Thanks,
Regina

________________________________

From: postgis-users-bounces at postgis.refractions.net on behalf of Simon Greener
Sent: Mon 6/18/2007 6:07 PM
To: postgis-users at postgis.refractions.net
Subject: [postgis-users] Centroid Within Multi Part Polygon



Someone asked recently about a centroid function which guaranteed that
the created centroid:

1. Fell within a polygon (not outside it as is the case with
implementations that average the X and Y coords of an area);
2. If the polygon is multi-part, put the centroid in the largest part.

I have just such a function but it is currently Oracle PL/SQL based. It
does both of the above + also have an overloaded version which will
return a multi-point object wherein each point is the centroid of each
disperate part in a multi-part polygon. The functions have been heavily
tested with many datasets and are pretty well guaranteed to work. I also
have a Java version.

I do not know PostgreSQL's implementation of PL/SQL but I suspect I
could convert the code pretty easily.  I do not have the time at the
moment to convert them but if anyone wants to download them from my
website (see below) and convert them please feel free. All I ask if for
a copy of the PostgreSQL implementation for hosting back on my website.

regards
Simon
--
SpatialDB Advice and Solutions Architecture,
Oracle Spatial, ArcSDE, Manifold GIS, Radius Topology and Studio
Specialist.
39 Cliff View Drive, Allens Rivulet, 7150, Tasmania, Australia.
Website: www.spatialdbadvisor.com
   Email: simon at spatialdbadvisor.com
   Voice: +61 362 396397
Mobile: +61 418 396391
Skype: sggreener
Longitude: 147.20515
Latitude: -43.01530
NAC:W80CK 7SWP3
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