15. Altimeter Basic Features
This watch is designed to calculate altitude from changes in barometric pres-
sure using the relationship between barometric pressure and altitude based on
the conditions of standard atmosphere*1. “Altitude Correction” is necessary to
ensure accurate display of the altitude while using this watch.
*1: Standard Atmosphere
Standard atmosphere refers to the “ICAO Standard Atmosphere” employed by
ICAO (International Civil Aeronautics Organization in 1964). It is defined as
having a barometric pressure of 1013.25 hPa and air temperature of 15°C at
sea level. Actual atmospheric states are constantly changing with time even at
the same location.
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If the watch is switched to the altitude measurement mode within
24 hours after the watch entered the surface mode, “SF.ck” is ini-
tially displayed for 10 seconds. The watch then switches to the
altitude measurement mode. This is displayed to urge the wearer
to check whether or not a suitable rest period has been taken
after diving, since moving to a high altitude soon after diving can
result in the risk of decompression sickness (bends).
Barometric pressure (hPa)
Altitude (m) Temperature (°C)
Temperature difference per 1,000 m
540.2
5,000
-17.5
616.4
4,000
-11.0
701.1
3,000
-4.5
Approx. 6.5°C
795.0
2,000
2.0
898.7
1,000
8.5
1013.25
0
15.0
Summary of Contents for C900
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