alt_baro: the aircraft barometric altitude in feet
alt_geom: geometric (GNSS / INS) altitude in feet referenced to the WGS84 ellipsoid
MLAT traffic tracks do not have the API alt_geom populated. This results in a CoT hae="9999999" value and does not work for 3D awareness.
For MLAT traffic tracks, if alt_geom is not populated, fail down to use alt_baro value, and calculate HAE based on:
Request a normal ADS-B aircraft with alt_geom within 25 NM of MLAT traffic of interest, compare the full ADS-B aircraft's alt_geom to alt_baro to calculate offset to apply to the MLAT target's alt_baro to get the missing alt_geom. Then use this "CALCULATED" geometric altitude in place of a missing alt_geom API value.
https://www.adsbexchange.com/version-2-api-wip/
MLAT traffic tracks do not have the API
alt_geompopulated. This results in a CoT hae="9999999" value and does not work for 3D awareness.For MLAT traffic tracks, if
alt_geomis not populated, fail down to usealt_barovalue, and calculate HAE based on:Request a normal ADS-B aircraft with
alt_geomwithin 25 NM of MLAT traffic of interest, compare the full ADS-B aircraft'salt_geomtoalt_baroto calculate offset to apply to the MLAT target'salt_baroto get the missingalt_geom. Then use this "CALCULATED" geometric altitude in place of a missingalt_geomAPI value.