Calibration

The altimeter's reference for turning pressure into height. Automatic downloads local weather for the device's position to fine-tune it, and falls back to the fixed values if the download fails.

Downloads current satellite orbit data (AssistNow) so the GPS gets a fix much faster. Each download is about 6 KB (0.006 MB); a shorter cache expiry keeps the orbits fresher but downloads more often.

Zeroes the rate bias on all three axes. Rest the board on a stable surface in the orientation it will fly in, then leave it untouched until the process completes. Typically takes 25 to 30 seconds to complete.

Removes the resting offset on both the low-g and high-g sensors. You will be asked to hold the board in six orientations; hold each steady until it is captured, then turn to the next.

Corrects hard and soft iron so the heading reads true. Slowly rotate the board through every orientation, turning it in all directions, until it completes. For the truest result, calibrate it fitted in the electronics bay exactly as it will fly, with the battery and everything else installed, so their magnetism is taken into account. Do it outdoors, well away from vehicles, buildings, mains power and any metal or electronics that will not fly with it, and keep phones, keys, magnets and metal off yourself while you turn it.

The offset between magnetic north and true north comes from the World Magnetic Model built into the firmware, using the device's position and date. A new model is issued every five years and arrives with a firmware update.