Mike, the new generation parking guidance systems will do that for you. We have just installed the new camera based system here at Canberra Airport.
Rather than use Infrared sensors above each bay, which often give a false vacancy, these use 4 cameras in each housing mounted in the aisle focused on each bay. So like the Tollway number plate readers they have the ability to gather all sorts of info, including your plate, then your parking position can be looked up at a kiosk or an app on your phone.
See link;
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