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<div class="moz-cite-prefix">Hi Pedro,<br>
<br>
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.<br>
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.<br>
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.<br>
<br>
Cheers,<br>
Tom<br>
<br>
On 19-7-2012 20:03, Pedro Doria Meunier wrote:<br>
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<font face="monospace">Hi,<br>
<br>
Need help/pointers on how to best construct the following:<br>
<br>
1 known point in a table. (call it buoy)<br>
<br>
another table containing the history (with a geom column) of
where a particular object (a boat) has been in time/space<br>
<br>
What I need to construct is a query that gives me the count of
how many times that boat has gone past that buoy.<br>
(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))<br>
<br>
Btw, both tables' geoms srid=4326.<br>
<br>
Any help highly appreciated ;)<br>
<br>
TIA,<br>
<br>
</font>
<pre class="moz-signature" cols="72">--
Pedro Doria Meunier
Telf. +351 291 933 006
GSM +351 917 999 236
Skype: pdoriam</pre>
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