note
Limbic~Region
[japhy],
<br />
The shortest distance between two points on a sphere (forget that Earth is squished a bit) is the arc of the great circle passing between those two points so you may have reason for concern. You should read [http://mathforum.org/library/drmath/view/51785.html|this] and [http://www.movable-type.co.uk/scripts/latlong.html|this] (Cross-track distance). You may find that treating the surface of the sphere as a flat plane acceptable if your talking about a small enough area - otherwise, you need non-planar math.
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Regarding your statement about MySQL query - I assume have no idea what built-in trig functions are available and I don't envy re-implementing them from scratch. If this were Pg, you could just use plperl and use the module that did what you wanted :-)
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Cheers - [Limbic~Region|L~R]
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