> Interesting, and I thought about it (I'm prone to brute force solutions).
> But since we need x/y info, these sensors (or beams) would have to be
> placed at the short _and_ the long walls, which would make it a bit
> cost-prohibitive. Also, the ground is sloping.

Here's a shot :
How about taking two of those laser pointing devices and pointing each
at a polished spinning axle with a flat surface on one side. You need
a few sensors along the walls. You know when a beam should hit the
sensors. A look-up table could do the rest.

-- 
Friendly Regards

Tjaart van der Walt
mailto:tjaart@wasp.co.za
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