roof top takeoff

[lougil]

Has anybody done this is there dangers that I need to know of such as elevation with gps?

 

[Pedals2Paddles]

If you're taking off from the flat rooftop of a commercial building or high rise, chances are there is a lot of steel structural supports in that roof. That can certainly induce some compass interference. I'm not saying it will, and I'm not saying don't do it. But it is a potential risk. If the roof is a steel deck of some kind, I wouldn't do it at all.