"Dave Butler" wrote in message
news:1114523965.843239@sj-nntpcache-5...
- GPS position calculation in the vertical axis has less precision than in
the
horizontal plane because of the geometry. A small error in measuring the
time of
arrival of the GPS signal translates into a larger error in the vertical
axis
than in the horizontal. Users' expectation that the altitude will be as
precise
as the horizontal location is misplaced.

Trivia (AIC): When a ship travels through the Panama Canal, it actually
gains/loses about 25 feet from entry to exit depending on the direction of
travel. Sea Level is not 100.0% level.