Yesterday I did some flying, latest app and firmware etc. and no problems. I had done a compass calibration, and all sensor values etc. were normal. I then walked about 500m to take off from a bridge (40m or 130 feet long) made from concrete and steel. I immediately noticed the I1 flying slightly erratically, saw an error message indicating compass and GPS error (despite 14 satellites) and noticed the rear light on the I1 flashing red and yellow. Realising the error of my ways, I immediately landed the craft assuming the bridge had effected the compass. I then proceeded to walk off the bridge recalibrate the compass and carry the I1 back to the bridge to take-off. As soon as I turned on the I1 the same error message appeared and the rear light was red/yellow again. My way around this was to leave the bridge, recalibrate the compass and FLY the I1 back to where I wanted to take some footage off to the side of the bridge and all was well. I did land the I1 on the bridge after 11 minutes of filming/flying and noticed the same error message appeared as the I1 touched down. It was a valuable lesson and I acknowledge I should have appreciated the likely influence of the bridge before take-off. My reason for posting this is twofold. Hopefully the information may assist others in learning more about safe flying and secondly to seek advice and assistance about flying from a boat. In August next year I am spending 2 weeks on a 5,000 ton, 120 passenger ship travelling around North Alaska and the East Coast of Russia towards Japan. Landings on the coast in Zodiacs will be done and flying the I1 from the shore will not be a problem after compass calibration. What can I do from the ship? I doubt that I can properly calibrate the compass on the ship’s deck. I will be clearly hesitant to take-off if I get the same error message that I had when I was on or had just taken off from the bridge. If the compass is calibrated on shore, is it possible to fly from the ship in the hope that the likely compass error will “correct itself” as I get some distance between the I1 and the ship? An alternative would be move a distance away from the ship in a Zodiac, calibrate the compass and take off from the Zodiac. I would be happy to get back on the ship with the I1 in the air before landing on the deck. Some months ago I had trouble getting the I1 to take-off from a fibreglass yacht, as the rocking of the boat seemed to upset the IMU. An error message resulted and the motors quite rightly didn’t start. I had heard that this “problem” had been corrected in a firmware update. I would be grateful for any assistance. I thank you in advance for spending the time getting through to the end of this long post. Hopefully in September next year I can post some great footage of the trip.