[postgis-users] ST_Collect

[Carsten Hogertz]

Hello,

I've got a question about using ST_Collect.

I have one table with hundrets of thousands of points. Within this table I
want to collect the points that are within a 500 meter radius and calculate
a convex hull around them.

Since the ST_DWithin needs (geom, geom, distance) and I only have one table
with points, do I first have to perform a self join to identify the points
within 500 meters and then a ST_Collect to group these points? Or can I
somehow do it without joining the one table with itself?

And can I use the ST_DWithin inside the ST_Collect? Like
ST_Collect(ST_DWithing(geom,geom,distance))?

Thanks for your help!
--
Carsten
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