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?
Best regards, Martin From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Oliver Monson Sent: Sunday, March 23, 2008 4:50 PM To: [email protected] Subject: [postgis-users] Filtering Points Based On Proximity Hi, I'm a very new PostGIS user but I need to solve a somewhat complex filtering problem (anyway I think its complex...) 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 squared area). 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. 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! -Oliver
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