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• https://mavlink.io/en/messages/common.html

• https://mavlink.io/en/messages/ardupilotmega.html

Reference frame

Global

Latitude and longitude: The origin is at the intersection of the Earth’s prime meridian and equator.

Altitude: The origin is at mean sea level.

Relative

North and east: The origin is at the drone’s home location.

Altitude: The origin is at the drone’s home location.