How come GPS reads different

Aluckyguess wrote:

I am getting over 500ft. difference and more.
"Matt Whiting" wrote in message
...

Aluckyguess wrote:

How come the GPS reads a different altitude than the Altimeter?

For many reasons. The main reason is that they derive altitude by two
completely different methods and this inevitably introduces errors. Then
each method has its own inherent errors.

Even two altimeters side by side won't read the same altitude other than
by accident.


Matt



GPS altitude is not accurate. That is why you need to have a baro sensor
included as input to a IFR approved GPS.

--
Regards, Ross
C-172F 180HP
KSWI

Ross Richardson wrote:

GPS altitude is not accurate.

.... except when it is, which is most of the time.

That is why you need to have a baro sensor included as input to a
IFR approved GPS.

That baro input is used as a cross-check for gross errors, to assist
RAIM. It does not "correct" inaccuracy, and thus is irrelevant to the
normal GPS altitude readout.


- FChE