As I am new to this forum, I want to introduce myself. I am fairly new to quads, but not to flying. I have my private pilots license (VFR, single engine) but haven't flown in quite some time, as it just got too time consuming and expensive (and lonely as my kids grew bored of flying with me). So after a few years away, I have moved on to quads. I have a couple of UDI 818A (my training birds), one still in the tree, and the second I just fished out of a huge foot-deep mud puddle, but it still flies. Now my new P3S in on the way, and I have some questions regarding calibrating the compass that the books and my research haven't yet answered. In much of my reading, it says to stay "away" or stay "clear" of large metal objects and magnetic fields. What I don't see is how far "away" and "clear" actually mean. Is it 10 feet away, 100 feet, 1000 feet? The next question is how big is "large"? Are we talking about power towers, TV antenna's, riding lawnmowers, or pie tins? Lastly, can I calibrate "away" from "large" metal objects and then fly near them later? I ask this as I have plans to do a lot of filming on the lake, In my mind I see a scene that starts on my boat dock (an open metal framed structure with a metal roof about 40'x30'). So can I calibrate it and launch direct from the dock? If not, can I calibrate on the shore and walk it out to the dock to launch? Or can I calibrate and launch from the shore and fly by at some distance to film it? I know this is long winded and I appreciate anyone who bothered to read this far, and appreciate even more anyone who will bother to provide input.