Blinky the Shark wrote:
>
> Mike wrote:
>
> > My Garmin Etrex Vista Cx has a built-in barometric altimeter, which
> > seems to be reasonably accurate (but is not calibrated over
> > temperature). It regularly changes by 20' or so in readings at the
park
> > where I begin and end my bike rides, between the beginning and end of
> > the ride. Typically, we start in the morning when it's cool, and
return
> > in the late morning or early afternoon when it's warm.
>
> So even leaving temperature out of the mix, how does a barometric
> altimeter sort out the effects of "meteorological" barometric pressure;
> how does one's barometer sort out the effects of altitude?
>
It doesn't. You gotta keep its setting updated during your
flight, and for sure, before you try to land. I reset the one in
my Olds to what I know is the terrain elevation where I park it.
That way, I don't have to check with Oakland air****t to get the
correct altimiter setting.
AUIU, above 20k ft (or so) everybody sets theirs to standard,
29.92" Hg IIRC. This keeps everybody on the same page, no matter
what the weather was when they left their air****t. Then when they
descend they get the latest correction from the destination
air****t.
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