A new project requires launching from a very large concrete garage roof, then flying up 300' and over 100' to show a building site and views. There is no other nearby launch point on the ground, and several nearby buildings add congestion. Any suggestions for safe ops, especially regarding the compass? Would it help to use a table-top on saw-horses, or on an aluminum ladder to get away from the rebar while powering up? Several cycles of power up - power down will be needed. Really hoping to NOT calibrate compass on site. Inspire 2 and also Mavic 2 Pro will be used. Thanks!