The CB antenna on the bullbar of my work Hilux is exactly 2.0 metres off the ground. Thankfully it's the highest point of the car. I drive into inner city caparks on a weekly basis with it and I've hit boards marked 2.1...
I've also cleared boards that say 1.95.. Probably depends on how the ramp enters the carpark a bit as well I should think.
I used to drive a Transit van for work which was 2.05 - I found a selection of car parks accross the city that I knew I could get in and out of and stuck to those. The way I found out was to drive in carefully with the Appentice hanging out of the van sitting on the window ledge with the window wound down so he could see the top of the van. :D

