I'll note here that this is not the right answer to the elevation "problem". I have another section on the altimeter that you ought to read. Once you understand how the altimeter works, you won't be itching to perform a reset to fix it, though performing a reset may be useful for other reasons. Maybe (I doubt it). But here is how, just is case.
Note that if you do a reset, you lose all your customizations and have to go through the whole setup process.
It is certainly better after the reset. It now shows 2398 (versus 2411 on the 66i). It is odd that it never seems to change, the values on the 66i do show some fluctuation. On a trip where I got up to 4500 elevation, I never saw a difference greater than 50 feet and 30 was the difference I usually saw.
I will note that my android phone shows the elevation as 2323, so the Instinct was doing as well (or perhaps better) even before I did the factory reset. The topo map shows 2400 feet.
It is pretty well know that elevation information from GPS is not that good. The error is typically 3 times the position error. One estimate is an error of from 35-70 feet. Another is that you should never expect better than 10 meters (35 feet).
To turn the phone on or off:
The reset takes quite a while (at least 2 minutes) while simply displaying "Garmin" on the screen. Then you go through a bunch of setup questions.
Tom's home page / tom@mmto.org