Hey man I'm a newbie, but keen to learn. Only had my P3 for a few days, but eventually will be flying off a boat (my home). Hate the thought of no control over the ocean. Where do I find that MOD value.I can't honestly say I know how the GPS works. But everything I've read is that a proper compass calibration will put the MOD value ~1500. If it's far away from that, then upon lift off, it will take off. A compass calibration is a reference point for the phantom. If your reference point is skewed on one of the coordinates, it will react. The gimbal also relies on that and if you look at some flyaway videos, the gimbal or horizon is lol over the place.
Case in point. I calibrated my phantom over an open field. I flew it three times. On the last flight. I set my phantom down about 15 feet from my truck and on concrete with rebar. I lifted off and it came right at me. I immediately shifted to atti mode, got orientation and height and then landed. My mod value was 1950. From then on, I always check that value before flight to know I have a proper compass calibration. It quick. And over 200 flights, I've only has one fly away that I was able to recover from. The one that taught me to look at the mod value there after. If you take anything away....do that
Norm