Detect OnGround Movements

[Tabum]

I'm looking for an algorithm to detect OnGround movements.

Even this sounds trivial, I think it is not.

Why?

o In the RBL-files often the Altitude is missing, but this is definitly no indication if the plane is in air or on ground.

o The "IF":   if ( Altitude<=AirportHeight ) then { PlaneIsOnGround }
also don't work always in a proper way, because sometimes the altitude is not exact.

Has somebody an idea how to solve this simple question in a simple way?

Thanks,
Tabum

[airman]

As Captain in airline, I was instructed that the transponder is no longer sending the altitude information below around 1000 feet radio altimeter, in order to avoid any RA or TA in short final due to false informations coming from aircraft standing by on threshold position.. It is why this information is not sending from the aircraft close to ground and on ground

[OKC-Steve]

The transponder has a squat switch signal that says we have weight on the wheels, and we are on the ground.  When that signal is active, the transponder switches to transmitting "I am on the ground" and it also changes the altitude to 0 feet.

I've watched my (competitor) receiver for a few years, and the aircraft always report barometric altitude until they are on the ground, then they transmit 0 feet. I admit this may be a program triggered thing.  That is, change altitude to 0 feet when you detect the squat switch active signal (it is transmitted on several downlink formats these receivers decode).

The competitor receiver also sends out an onground boolean true on the TCP port 30003 for the aircraft.  I don't know if RB uses that boolean.

You are supposed to get TCAS alerts anytime you are flying.