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<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>Not sure how to do a radius search in PostGIS but you will
definitely need to use the geos DISJOINT function somehow to get points outside
your circle. Maybe start with a rectangle and do a search for radius query.
Hope that helps somewhat. Maybe it can be combined with a DISTANCE from your
center point?<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:10.5pt;font-family:Consolas;
color:#1F497D'>Best regards,<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:10.5pt;font-family:Consolas;
color:#1F497D'>Martin<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
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<p class=MsoNormal><b><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'>From:</span></b><span
style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'>
postgis-users-bounces@postgis.refractions.net
[mailto:postgis-users-bounces@postgis.refractions.net] <b>On Behalf Of </b>Oliver
Monson<br>
<b>Sent:</b> Sunday, March 23, 2008 4:50 PM<br>
<b>To:</b> postgis-users@postgis.refractions.net<br>
<b>Subject:</b> [postgis-users] Filtering Points Based On Proximity<o:p></o:p></span></p>
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<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>Hi, <br>
I'm a very new PostGIS user but I need to solve a somewhat complex filtering
problem (anyway I think its complex...)<br>
<br>
I have around 300,000 points, each with a lat, lon and altitude (also converted
to geometry). I need to get a subset of those points, where none of them are
within 5m (or some other arbitrary distance) of each other. It doesnt matter
which points get picked over another, as long as whatever the data set it
creates, that none of the points are within that 5m radius and that relatively
most of the points are used (the points are scattered across a 20km<span
style='font-size:10.0pt'> squared area)</span>. I have other data like a
timestamp for each point so I can give priority to the more recently created
points, if that helps as a starting point. If it makes it any easier, the
altitude can be ignored and we can treat it as a set of points on a 2D plane. <br>
But how would I go about doing this? I really have no idea where to start. What
would the SQL query look like? Any help would be appreciated, thanks!<br>
<br>
-Oliver<o:p></o:p></p>
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