What drives the altitude on the Passenger inflight display?
Landed at Nice with Swiss and the inflight display showed altitude of minus 25m just before we landed, followed by a firm landing and then an altitude of (+)8m.
Is this driven off the same source as cockpit instruments? and if so does it indicate an altimeter fault, or does the software look at the RoD and extrapolate the height at the next refresh?
Apologies if question is not 'tech' enough.