Hi Pedro,
You might try to create lines from the boat tracks (see examples in
manual for ST_MakeLine) and circles (st_buffer) from the proximity
areas around the buoy.
Now do a ST_Intersection(boatline, bouycircle). The result should be a
set of lines within the bouycircle. Every line stands for one pass along
the bouy.
I think ST_Intersection might result in a geometry collection of lines
and points so you would have to make a dump of the result with ST_Dump
and then select only the lines.
Cheers,
Tom
On 19-7-2012 20:03, Pedro Doria Meunier wrote:
Hi,
Need help/pointers on how to best construct the following:
1 known point in a table. (call it buoy)
another table containing the history (with a geom column) of where a
particular object (a boat) has been in time/space
What I need to construct is a query that gives me the count of how
many times that boat has gone past that buoy.
(there *will* be more than 1 rows giving proximity of the object to
the buoy -- need to get rid of those ;) -- since the boat is slow
moving (2-10 knots))
Btw, both tables' geoms srid=4326.
Any help highly appreciated ;)
TIA,
--
Pedro Doria Meunier
Telf. +351 291 933 006
GSM +351 917 999 236
Skype: pdoriam
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