[postgis-users] Closest point problem(s)

[Thurber, Fred]

I think I need to clarify my previous post. It is really two-part.  Here is the first part:

Closest point problem:
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Given a point, find the closest point in our data to it.  I was thinking of a query such as this from an old posting (http://postgis.refractions.net/pipermail/postgis-users/2005-June/008262.html):

SELECT the_point
FROM foo
ORDER BY distance(the_point, GeomFromText('POINT(-80 45)', -1))
LIMIT 1;

But this must doia full table scan  The post had a way to first get a bounding box and then do the distance query to cut down the search size (http://postgis.refractions.net/pipermail/postgis-users/2005-June/008262.html):

SELECT the_point
FROM foo
WHERE the_point && 'BOX3D(-180 -55, 20 145)'::box3d
ORDER BY distance(the_point, GeomFromText('POINT(-80 45)', -1))
LIMIT 1;

Is there a better way to do this?


A lot of closest point problems:
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My second question is this: I will be running this query 100-200 times, once for each item in my query.  We are modeling a ship steaming in a straight line, every 5 miles we will want to find the closest point in our data to the ship.  Is there a way to do this query in one step instead of solving 100-200 closest point problems?


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