The difference at Heathrow? They have installed digital cameras pointing at every parking slot, and these are setup to do number plate recognition. Outside the elevator is a little computer kiosk with a sign "Locate your car." Type in your number plate, and the kiosk will find your car, show you a picture and direct you to it! Pretty cool idea. No idea how well it works, but I overheard people in the car park who were also pretty impressed by the service.
I would seem though that the real reason for the technology is tracking payment. The system can monitors who has paid and not paid digitally. When you go to the pay booth/ kiosk, you enter your license plate, it shows you a picture and you pay for your parking. No need to display a ticket in your window any more. And the system knows when you arrived and when you left. No need to have any poorly paid meter maids or parking enforcement employees. Park and don't pay? The system will use your car's number plate to access your address, and send you a parking fine/ violation in the mail.
I saw this technology in use all over the UK. In other pay and display car parks (Oxford Park & Ride), and the City of London uses license plate recognition to enforce its Congestion Fee, which is assessed on all vehicles going in the center of London during peak hours (mainly day time).
Not sure if any of the public had any concerns about the privacy implications. My first thought was who gets access to this data, and why? The UK is the most digital and CCTV monitored population in the world. And it seems to be getting worse. Austerity measures after the global recession have resulted in huge cuts to government services and programs. There are fewer police to enforce the laws and consequently an ever increasing reliance on technology to do the work. Police departments now have technicians sitting in control centers watching hundreds of video feeds looking for anything that warrents sending a car. If this sounds Orwellian to you, then you are of the same mind as me. Don't know Orwellian? Download "1984" by George Orwell and read it!
Ultimately the use of number plate reading technology in car parks will become common place where the business can justify the cost, and the cost continues to drop. Unfortunately in this case it means laying off (or reassigning) people checking parking stickers. But there will be an additional administrative cost dealing with customer service complaints and corrections where the technology misses the mark. Where the technology works well, the public will accept it. Of course the converse is also true and leads to public outrage. I will cover a "fail" example next.