At 01:02 PM 8/12/2010 Thursday, Shawn Wright wrote:
>I've often thought having an altimeter in the van would be a useful addition
>when driving in the mountains, as knowing the elevation of a pass doesn't
>tell the whole story if you don't know your current elevation. Has anyone
>tried one with any success?

Standard barometers lose just about one inch per thousand feet, so if
you correct one to sea level and know the local barometer reading you can tell.

GPS with three or more satellites in view can tell altitude with a
system spec of +/- 100 feet.

Aircraft-type pressure altimeters are really cool, and really expensive.

A water barometer is about 13 times as sensitive as a mercury one,
and you can fake the fifty-foot column with a semi-evacuated tin
can.  Probably not a dashboard installation though.

Little silicon sensors are getting more common and cheaper, so more
and more little things will have them.  They still need to have a
starting point to calibrate from, though, like any pressure-measuring device.

d