Posted by Brian Dunning on 10/03/48 11:05

>> I realized one day that at a distance of a hundred miles or less, I
>> just
>> didn't *CARE* about curvature of the earth, and replaced that trig
>> with
>> your basic Cartesian distance.

True, but be aware that this is only true when all of your coordinates
are in the same general latitude. For example, lines of longitude are
much closer together in Montana than they are in Texas.

>> If tomorrow the USPS creates zip code 60609, I can be
>> pretty damn sure it's "close enough" to 60601 through 60608 and just
>> average them to make up bogus long/lat. Sure, it's "wrong". It's
>> also
>> FREE and "close enough" for what I (and almost for sure you) are
>> doing.

As the purveyor of a zip code database, I can assure you that this is
not at all true. In many cases it is, but in many cases, not. Example:
Here in So Cal we have 8 new zip codes since last month where the
nearest zip code numerically is over 25 miles away.

But I hear what you're saying as far as "good enough" for this
particular application.

- Brian

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