How to measure direction the car is coming to garage door?
It is very hard to determine position accurately there is a new project on kickstarter called Pozyx, you can look at that but that's expensive, to be honest this sounds like a job for hanging tennis balls or strings or something like that. But if you have a lot of money to blow and you just want a project go for it, you may be able to do this with ultrasonic sensors but I reckon that would be painful. Anyway good luck