How do I figure out my height?

I have two antennae on the front of the coach that are just higher than any other high point. If I am suspicious I will slow down to less than a walk an see if they hit. If so I can stop, disconnect the tow'd and back out. This only applies if I have not had other warning of low clearance. I had my coach measured by Escapees when I was having it corner weighed. they have a truckers pole with a horizontal bar on the top. With the coach on their level platform, they lower that to touch the high point and read the height off the scale. 12'6" I am sorry that is such a mundane approach it even eliminates arithmetic from the operation.