Compass Calibration!

ardupilot.org/copter/docs/common-magnetic-interference.html

  1. Many things can distort the earth’s magnetic field in the area you are flying:

    • Steel framed or reinforced concrete buildings, bridges and roadways, iron pipes and culverts, high power electric lines, heavy equipment, trucks and automobiles, steel tanks, electric motors and even computers.
    • Flying between steel framed or reinforced high rise buildings will distort the magnetic field in addition to causing GPS multi-pathing.
  2. Safe distances for compass calibration

    • 6” (15 cm) minimum: Metal rim glasses, pen/pencil, metal watch band, pocket knife, metal zipper/buttons, belt buckle, batteries, binoculars, cell phone, keys, camera, camcorder, survey nails, metal tape measure.

    • 18” (50 cm) minimum: Clipboard, data collector, computer, GPS antenna, 2-way radio, hand gun, hatchet, cell phone case with magnetic closure.

    • 6 ft (2 m) minimum: Bicycle, fire hydrant, road signs, sewer cap or drain, steel pole, ATV, guy wire, magnets, chain-link fence, bar-wire fence, data collectors

      that use a magnet to hold the stylus.

    • 15 ft (5 m) minimum: Electrical box, small car/truck, powerline, building with concrete & steel.

    • 30 ft (10 m) minimum: Large truck, metal building, heavy machinery.