On Tue, 19 May 2009, Mark Burton wrote:
Well, that's a good question. As distance() mostly gets called to
determine which of a bunch of points is nearest, it probably doesn't
matter at all that the result is slightly "wrong".
Really? In that case you could as well change the metric from Euclidean to
something more simple like the Manhattan metric:
dist = abs(lat2-lat1) + costab[lat1] * abs(lon2-lon1)
where costab is a table lookup for cos(). This will still find a point
that is close, but it is not guaranteed to be the same as with the
Euclidean metric. Would that matter?
-Wolfgang
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