> Looks like somebody's aready done
> an RF - acoustic location "thing"
> with resoulution to 12.7mm over 9.1 M^2
>
> -Monta
snip...
> active beacon. Inter-robot commu-nication is accomplished over the
> same spread-spectrum channel using a time-division-multiple-ac-cess
> scheme controlled by the base station. Principle sources of error
> include variations in the speed of sound, the finite size of the
> ultrasonic transducers, non-repetitive propagation delays in the
> electronics, and ambiguities associated with time-of-arrival
> detection. The cost for this system is $10,000.
>
At that price let's get two!!