GPS altitude & indicated altitude differs

[kf6iat]

Related question... do others see a difference between the Altimeter reading and the GPS altitude shown on a system like Garmin Pilot??.. When flying there is always a difference between what I see on Garmin Pilot, and the properly set Altimeter. 500 to 800 ft difference... I only use the Altimeter as my go by, just wondered why there is that much of a change in the 2 systems..

ATC is reading the encoder at the same as my Altimeter, and the system was checked and certified last year when I purchased the plane..

 

[FlyCanadianGuy]

 

[Orest @ CYFD]

 

[skywag]

 

[EchoDelta]

 

[kshaw]

 

[kf6iat]

 

[Flying_Monkey]

 

[EchoDelta]