No altitude on some aircraft, but it exists

[Ressy66]

Occasionally I see some aircraft not reporting alt, seem to be older aircraft, however, a quick test of MalcolmRobbs fork, and it reports it! quick kills' and restarts between the two confirm Antirez's version not decoding it, but Malcolm's does, its also been over several aircraft, tested over several days, so not sure where Malcolms changes get this but obviously I report it as a bug since the "upstream" parent/master/actual code devs version, does not.

I execute both binaries identical : dump1090 --net --interactive --aggressive

Example, aircraft VH-LEM

Antirez

DF 17: ADS-B message. Capability : 5 (Level 2+3+4 (DF0,4,5,11,20,21,24,code7 - is on airborne)) ICAO Address : 7c384c Extended Squitter Type: 4 Extended Squitter Sub : 1 Extended Squitter Name: Aircraft Identification and Category Aircraft Type : Aircraft Type A Identification : LEM

DF 17: ADS-B message. Capability : 5 (Level 2+3+4 (DF0,4,5,11,20,21,24,code7 - is on airborne)) ICAO Address : 7c384c Extended Squitter Type: 11 Extended Squitter Sub : 0 Extended Squitter Name: Airborne Position (Baro Altitude) F flag : even T flag : non-UTC Altitude : 0 feet Latitude : 77568 (not decoded) Longitude: 70581 (not decoded)

DF 0: Short Air-Air Surveillance. Altitude : 0 feet ICAO Address : 7c384c

MalcolmRobb

DF 17: ADS-B message. Capability : 5 (Level 2+3+4 (DF0,4,5,11,20,21,24,code7 - is airborne)) ICAO Address : 7c384c Extended Squitter Type: 4 Extended Squitter Sub : 1 Extended Squitter Name: Aircraft Identification and Category Aircraft Type : A1 Identification : LEM

DF 17: ADS-B message. Capability : 5 (Level 2+3+4 (DF0,4,5,11,20,21,24,code7 - is airborne)) ICAO Address : 7c384c Extended Squitter Type: 11 Extended Squitter Sub : 0 Extended Squitter Name: Airborne Position (Baro Altitude) F flag : even T flag : non-UTC Altitude : 10500 feet Latitude : -26.449219 Longitude: 152.823970

DF 0: Short Air-Air Surveillance. VS : Airborne CC : 0 SL : 0 Altitude : 10500 feet ICAO Address : 7c384c

[Ressy66]

Something thats been suggested, is MalcolmRobbs understands msgtype 18, Antirez, your version does not? can't find it in code, perhaps this the problem?