The barometer's ground level was set again
What ArduPilot says:
- Barometer calibration complete
- Updating barometer calibration
The ground station, or a calibration screen on the transmitter, asked for a barometer calibration. ArduPilot takes the pressure it measures now as ground level, so the altitude reads zero here; the two lines mark the start and the end. On a plane with an airspeed sensor the same request also starts the airspeed zero calibration: cover the pitot tube from the wind while it runs.
The code that sends it
Barometer calibration complete
libraries/AP_Frsky_Telem/AP_Frsky_MAVliteMsgHandler.cpp AP_Frsky_MAVliteMsgHandler::handle_command_preflight_calibration_baro() · Open in ArduPilot Copter-4.7.1
libraries/GCS_MAVLink/GCS_Common.cpp GCS_MAVLINK::_handle_command_preflight_calibration_baro() · Open in ArduPilot Copter-4.7.1
Updating barometer calibration
libraries/AP_Frsky_Telem/AP_Frsky_MAVliteMsgHandler.cpp AP_Frsky_MAVliteMsgHandler::handle_command_preflight_calibration_baro() · Open in ArduPilot Copter-4.7.1
libraries/GCS_MAVLink/GCS_Common.cpp GCS_MAVLINK::_handle_command_preflight_calibration_baro() · Open in ArduPilot Copter-4.7.1