About?
You don't need to know "about."
Sorry, but you need to measure while it is hooked up to the tow vehicle. 1 inch can make a "crunch" of difference. The easiest way is to have someone else do it, like I did. I used a laser level. leveled it at the highest point and let it hit the tape measure that someone is holding on the ground and the person on the roof has the large number end.
But, I guess you could always say that the approaching bridge is "about" 13' 5"
