Often when i compare FR24 displayed MLAT aircrafts (ModeS) and compare with my own direct received values, i see some strange differences.

There can easily bee 3 times difference in ground speed and IAS. An example i'm looking at now, shows GS=170 and IAS=753 kts, and the aircraft is not sending any speed indication, so i guess both are calculated values. Wonder why 2 values are actually displayed if both are calculated?

There can also be a major difference in Calibrated and GPS altitude. Calibrated is the one from the transponder, and the same i receive. GPS must then be the calculated one? And why also display the calculated one when you have the transponder altitude?

Just optimising if calculations are not needed :-)

br Lars