Drone pilots of all stripes know the routine when arriving at a location, unpacking their drone, setting up to launch, and then getting the dreaded compass error. This usually results in the operator having to do an awkward dances with the drone routine. In public safety situations where time is of the essence (such as trying to track an active shooter or assessing an apartment fire), drones provide an invaluable level of situational awareness and “eyes in the sky”, so being able to deploy them as soon as possible is critical to a positive outcome. In this post, we’re going to explore when and why to calibrate your drone and tips for getting in the air much faster.
Compass calibration on a drone is done to align the drones’ flight system with the Earth’s magnetic north, not its true north. This phenomena is known as magnetic declination and accounts for the Earth’s shifting magnetic field (typically by a large number of degrees to that of true north). An algorithm stored in the rom memory of the aircraft accounts for this delta and allows for proper calibration of the magnetometer, the drone’s electronic compass. This magnetometer in conjunction with other onboard sources (GPS, gyros, accelerometer, altimeter) accurately determine its spatial positioning and are critical in generating precise flight control. Problems with calibration are often the main reason for dreaded fly-aways.
So when should you calibrate, and more importantly not re-calibrate your UAS’ magnetometer? You should always calibrate before an aircraft’s first flight to feed accurate positioning data into the flight system. Additionally, you should calibrate if you were flying in Texas and now want to fly in California as there will be much declination. However, if you’re in your hometown or roughly less than 250 miles away from it, you should not need to calibrate. If you are getting calibration errors in this instance, first try moving your aircraft to a soft patch of grass and away from ferromagnetic or electromagnetic sources such as rebar, drainage pipes, underground power lines, irrigation systems, and rocks.
The process of calibrating your drone can take several minutes (and frankly looks silly!) so knowing when to calibrate and not calibrate your UAS and being able to identify potential sources that could affect the magnetometer can help save valuable time when on-scene.
As always, keep flying safe!