Decoded ADS-B airborne velocity (BDS 0,9, type code 19). Ground-speed
subtypes report true track; airspeed subtypes report magnetic heading -
airspeed messages are transmitted when the aircraft lacks a good
GPS-derived track and falls back to its compass heading instead.
Decoded ADS-B airborne velocity (BDS 0,9, type code 19). Ground-speed subtypes report true track; airspeed subtypes report magnetic heading - airspeed messages are transmitted when the aircraft lacks a good GPS-derived track and falls back to its compass heading instead.