Originally Posted by
cplager
If you have a GPS by itself, that almost certainly isn't true. Mobile GPS units have notoriously bad altitude.
The higher end Garmins use barometric pressure to get a more accurate result, but that is sensitive to changing weather.
Not my experience. Changing weather will only change it by maybe 100'. I get very accurate repeatable readouts from my Edge 800. Very accurate meaning compared with the estimate from any mapping website. You've had a different experience?