Tuesday, August 24, 2010

Pythagoras ~ Correction

No, not to his theorem, but to my use of it.

FSS has pointed out that my method of arriving at the distance between two grid references is flawed when the two points are in differently lettered 100km squares. Lancashire as far south as Bolton, west into the Irish Sea, north as far as South Lakes and east into Gordonland is all in square SD, so it works for all this area.

But when the two points straddle a vertical boundary, you need to put a 1 in front of the more eastern first three numbers and when they straddle a horizontal boundary put a 1 in front of the most northerly second three numbers.  If they straddle both, put a 1 in front of both ~ simples?

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