ADS-B altitude reporting

[NYTOM]

The responses have been very educational. I’m sure everyone is right about the on-line flight reporting services and their lack of accuracy compared to actual flight. In my ignorance I assumed all readings would be close if not the same. What brought this all to light was my concern for what altitude others were seeing me at in their cockpits. On nice days it can get pretty crowded on the East Coast and although I don’t totally rely on it , it’s nice to have a second set of electronic eyes watching for traffic. I WILL check it out with ATC on the next flight .

[GalinHdz]

As I said before:

Originally Posted by GalinHdz

GPS altitude is best for not colliding with things on the ground. Barometric altitude is best for not colliding with other aircraft.

[BobTurner]

I think most adsb-in systems don’t display target altitudes. Since adsb data contains both gps altitude and pressure altitude, the system displays an apples to apples difference: either the difference between target gps altitude and on-board gps altitude, or the difference between pressure altitudes. It then displays targets as 100’ higher, 200 ft lower, etc. Either data difference should be accurate, easily understood, and you don’t have to worry about actual indicated altitude.