> Make a giant sized magnetic barcode and stick one on the side of each car.
>   A 2 foot by 3 foot barcode should be readable from several feet, no?

Railways use these. Readable from a  distance

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Cars have receiver which sees a beacon (eg laser line).
Car then transmits it's ID and a local clock AFTER passing line for several
iterations with random pause between. Could be done with eg IR.
Could have several trigger points on track.
Needs uP in car.
Needs timing in car.
Needs receiver (one per trigger point)
Not overly complex.

As long as car clock is stable enough for period of race the absolute clock
value is irrelevant - it self calibrates after the first reading.
Tlap = Clock_now - clock_then.

100 f/s = 10 ms resolution for 1 foot timing.
= 1 mS for 0.1 foot timing



        RM

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