N7 Autopilot User Manual (ArduPilot) v1.0
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⚫ Alt disparity: the barometer altitude disagrees with the inertial navigation (i.e.,
Baro + Accelerometer) altitude estimate by more than 1 meters. This message
is normally short-lived and can occur when the autopilot is first plugged in or if it
receives a hard jolt (i.e., dropped suddenly).
⚫ Compass not healthy
⚫ Compass not calibrated.
⚫ Compass offsets too high: the primary compass’s offsets length (i.e.,
sqrt(x^2+y^2+z^2)) are larger than 500. This can be caused by metal objects
being placed too close to the compass. If only an internal compass is being used
(not recommended), it may simply be the metal in the board that is causing the
large offsets, and this may not actually be a problem in which case you may wish
to disable the compass check.
⚫ Check mag field: the sensed magnetic field in the area is 35% higher or lower
than the expected value. The expected length is 530 so it’s > 874 or < 185.
Magnetic field strength varies around the world, but these wide limits mean it’s
more likely the compass calibration has not calculated good offsets and should
be repeated.
⚫ Compasses inconsistent: the internal and external compasses are pointing in
different directions (off by >45 degrees). This is normally caused by the external
compasses’ orientation (i.e., COMPASS_ORIENT parameter) being set
incorrectly.
⚫ GPS Glitch: the GPS is glitching and the vehicle is in a flight mode that requires
GPS (i.e., Loiter, PosHold, etc) and/or the cylindrical fence is enabled.
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