Effect Of Air Temperature On Altitude Measurement - Suunto ADVIZOR Manuel D'instructions

7.6 COMPASS
The purpose of the rotating bezel is that people can use the instrument as a regular base plate compass if they
want to, and use the bezel to e.g. indicate North when in the bearing tracking mode or leaving the compass
display for another mode.
Also, it can be used to manually follow your vertical progress by using the North indicator on the bezel to mark
the altitude from where you want to follow your progress (i.e. a zero point). You could also mark a certain
altitude, which is graphically shown by the segments on the circumference, to get an intermediate difference
measurement. However, the bezel is mainly related to the compass function.
Local declination, either E or W, is usually marked on maps with either one-degree or half-degree accuracy.
7.7 EFFECT OF AIR TEMPERATURE ON ALTITUDE
MEASUREMENT
The atmospheric pressure means the weight of air mass above the observer: at a higher altitude there is less
air than at a lower altitude. The principle of an altimeter is to measure the different air pressure between
different altitudes.
The air weight is affected by the outside temperature. Consequently the air pressure difference between two
altitudes is also dependant on temperature.
The altitude calculation of Wristop Computer is based on the air pressure at certain normal temperatures. Each
altitude has a definitive normal temperature. The normal temperatures at each altitude are presented in table 1.