SUUNTO AMBIT2 R User Guide - Manual (Page 56)

Absolute air pressure and known sea level air pressure = Altitude
Changes in local weather conditions will affect altitude readings. If
local weather changes often, it is advisable to reset the current
altitude reference value frequently, preferably before starting your
journey when the reference values are available. As long as the
local weather stays stable, you do not need to set reference values.
9.3 Getting incorrect readings
ALTIMETER profile + standing still + weather change
If your Altimeter profile is on for an extended period of time with
the device in a fixed location while the local weather changes, the
device will give incorrect altitude readings.
ALTIMETER profile + altitude moving + weather
change
If your Altimeter profile is on and the weather changes frequently
while you climb in altitude or go down in altitude, the device will
give you incorrect readings.
BAROMETER profile + altitude moving
If the Barometer profile is on for an extended period of time as you
climb in altitude or go down in altitude, the device assumes that
you are standing still and interprets your changes in altitude as
changes in sea level air pressure. It will therefore give you incorrect
sea level air pressure readings.
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