If you manage parking at an airport, you'll understand that airport parking can be full of specific headaches. Whether it's free or paid parking, whether the airport is large or small, whether it's a long-term airport parking lot or a kiss-n-ride bay, there are always people who park where they shouldn't, park too long in the short-term parking, etc.
What it all boils down to is compliance. You need people to follow your parking rules. But in order to create compliance, you need to know who is parking badly... and you need to keep track of repeat offenders.
And that's where handheld license plate recognition (LPR) comes in.