"Tauno Voipio" wrote in message

Yes - it's called the reference ellipsoid. There are actually
several of them and some GPS receivers allow selecting your
favorite one.

Interesting.

Actually, if Earth would disappear with all its mass, GPS would
get unusable, as the satellites would continue out of their
tracks due to the lack of gravity pull.

Yeah, but they'd work longer than a pressure altimeter so I think we should
still adopt GPS altimeters in case this ever actually happens.

--
Jim Fisher