How does a 76csx determine altitude

I know it has a pressure sensor, but it's not like an aircraft
altimeter, so I can't set sea-level base pressure. Does it smooth the
vertical portion of the GPS output with the barometer? Is there a way
to ignore the barometer so that it works inside of a pressurized
aircraft?

While on the satellite page select menu, then "GPS elevation"

NadCixelsyd wrote:

Change the Barometer Mode from "Variable Elevation" to "Fixed Elevation."

This implies that changes in pressure are not changes in elevation so
the receiver uses the GPS elevation instead of the output from the barometer.

This doesn't work on some earlier Garmin receivers.

With the Barometer Mode set to "Variable Elevation" the receiver uses the
GPS elevation to slowly calibrate (assuming Auto Calibration is set to "ON")
the barometer which then supplies the elevation. The GPS elevation varies
a lot short term but its long term average is good. The barometric elevation
is fairly stable short term but its long term accuracy is not so good. So
the GPS elevation is used to correct the long term accuracy of the barometric
elevation.

--
Dan

Personal: www.gpsmap.net
Business:
Western Maps LLC
www.westernmaps.us

The barometric elevation
GPS elevation is used

So, excluding usage in aircraft, what kind of accuracy are we talking
here. Assuming the 76csx has been on for a while how accurate is the
altimeter? three feet? five feet? ten feet? And how long does the
unit have to be on to obtain that accuracy? Are the measurments
relative to the geoid or to the WGS84 sphereoid?

On Wed, 9 Dec 2009 10:25:11 -0800 (PST), NadCixelsyd wrote:


Plus or minus several dozen feet instant read. (I've seen a GPS-source
altitude reading drop 50 feet while the receiver was sitting on a picnic
table, over the course of about two minutes.) You'd probably need 20-30
minutes at a given elevation to "calibrate" the pressure-based altitude
measure.

--
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the chance to reject a job as my trusted lieutentant, I will retain
enough sanity to wait until my current trusted lieutenant is out of
earshot before making the offer. --Anspach's Evil Overlord List