Drone Compass Calibration: Lessons from the field

Lessons From the Field: Compass Calibration

It comes without surprise that with travel and meeting many of you that I find myself in conversation with UAS pilots across the globe. All too often I become aware of operators that infrequently or improperly perform compass calibrations for their aircraft... be it the DJI Phantom UAV series, or any other. In each of these cases, the potential for disaster is significant (see the first two installments of my escapades in Iceland), and what makes this even more troubling is that getting drone compasses up to par is easy so easy to do, and really comes down to being a free insurance policy.

Going airborne with unmanned aerial vehicles with incorrectly-tuned compasses has been the single largest contributor to so called “fly-aways” and unfortunately in many of these cases the uninformed have just naturally tagged the drone manufacturer with blame of problematic equipment. Short of “fly-aways”, customers with poorly tuned drone compasses tend experience drift, varying unresponsive control(s) and exaggerated pitching during take-off.

Drone compasses can become detuned from any magnetic and RF source. Perhaps the most common cause is getting aircraft too close to speaker magnets as drones are often transported in vehicle passenger cabins and trunks. Vehicle radio speakers, that are within range of just a couple of feet is enough to throw a compass out of kilter. Aside from magnets, source of RF power such as mobile radios and base stations emit plenty of power to trouble drone navigation systems.

As an avid drone pilot myself and having experienced and overcome these issues, calibrating multirotor compasses is always on my preflight checklist. Short of calibrating a compass prior to each and every flight, here are top triggers that demand a compass calibration:

  1. Change in location, especially east and west
  2. Close proximity to magnets or strong RF sources
  3. Previous flight in inclement weather
  4. Abnormal flight activity such as high wind and hard landings

When performing proper UAV compass calibrations, here are the fundamental requirements:

  1. Perform outdoors (recommended to perform on lawns, bare earth and asphalt)
  2. Be free from all magnetic metal (watch out for rebar found in concrete)
  3. Be away from both underground and overhead powerlines
  4. Precisely follow manufacturer’s guidelines specific to your aircraft

With most drone aircraft, if you’ve followed compass calibration procedures you should see some type of visual confirmation that the calibration was successful and within a safe margin for flight. If for some reason no success confirmation present itself, then I recommend not-flying and using supplied software diagnostics to learn why the procedure failed.

In the case of DJI products such as the Phantom UAV drones, failed compass calibrations is typically because of compass has gone too far out range that a full compass reset is required. For instance, as shown below, the MOD value of a Phantom should always read in the range of 1400 to 1800. If this value is outside of the range by hundreds, then a simple calibration will solve the problem. If its off by thousands, then a full compass reset or replacement is required. For resetting your compass, please see the below video.

It’s my mission to make sure your successful in all your airborne missions with drones. Should you have any questions, please feel free to drop me a line at eric@uavdirect.com Also, please sound-off with any comments or suggestions for future blogs.

Thanks reading,

Eric




Joel J.
Joel J.

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