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Barometer vs Ambient Pressure Data Field

Hi guys,

I have a GPSMAP 66 and come across two different data fields, barometer and ambient pressure. I know the ambient pressure is the actual static pressure the sensor is sensing, but what is barometer pressure? I thought it refers to the sea level pressure which I calibrate the altimeter to but it doesn't seem to be the case.

On aircraft altimeter, there is a Kollsman window which we can put in local altimeter setting from the airport (sea level pressure setting calibrated for non-standard pressure and temperature). This is basically how I calibrate the GPSMAP 66's barometric altimeter. The altimeter basically measures the difference between "ambient pressure" and "sea level pressure" and converts the pressure difference into "elevation"(true altitude in MSL).

The "barometer" term would be mind-boggling if it refers neither to "altimeter setting" in aviation nor "atmospheric pressure". Can someone share any insights?