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Re: New openGIS functionality in MySQL available for testing
Posted by: John Powell
Date: April 21, 2008 06:46AM

Actually, the answer is 44.05 if you apply pythagoras's theorem to those 4 numbers. However, your point is a good one. The answer depends on the spatial reference system used when you create the geometry objects in question. The haversine formula is used for coordinates that are in lat/long, whereas pythagoras's theorem can only be used for coordinates that have been projected onto some local coordinate system.

As far as I know, MySQL does not currently take into account the spatial reference system when calculating distance. Your best bet would be to write your own custom distance function using haversine's formula. I have been tempted to write my own and submit it to MySQL, but have been so swamped by my current project (ironically, in lat/long) that I haven't even had time for further testing of the new GIS features this thread is about.

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