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Press either the [SELECT] or the [MODE] button to exit this activity.
Clearing the Logbook History
To clear the history of the logbook:
1. In any of the logbook history screens, press the [SELECT] button for 2 seconds. The top
field displays the text CLR, the middle field the text HIS, and the bottom field the text
nO. All three messages will begin to flash.
2. Press either the [ON OFF] or the [QUICK] button to toggle between YES and nO.
3. Press the [MODE] button to accept the preference YES and exit.
The logbook history is erased and a new starting date will be set to begin new cumulative
measurements.
NOTE: Setup mode will automatically exit if left idle for more than one minute.
We recommend that the logbook history be cleared prior to beginning logbook recording(s).
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 outside temperature affects the air weight. Consequently the air pressure difference be-
tween two altitudes is also dependant on temperature.
The altitude calculation of the Observer is based on the air pressure at certain normal tempera-
tures. Each altitude has a definitive normal temperature. The normal temperatures at each alti-
tude are presented in Table 1.
The altitude measurement error caused by an abnormal temperature gradient can be approxi-
mated as follows. If the sum of the temperature offsets from the normal temperatures
determined at two different altitudes is 1 ºC, the altitude difference calculated by the
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