GPS altitude again is close to actual

Mxsmanic wrote:
writes:

While correct for the case of LAAS and DGPS, this is not correct in the
case of WAAS.

It's true for WAAS, too. WAAS has only a few fixed reference points
and extrapolates for all other points

You don't understand how WAAS works.

You stated:

" The further away you are from the surveyed reference
position used to generate the corrections, the more likely it is that
your position will be incorrect."

This is false. Being inside the reference network is all that matters,
proxitimity to a WRS does not matter.

Regards,
Jon