CatEye AT-110 [Altimeter] - Manual (Page 13)

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5. Altitude Correction
Atmospheric pressure changes constantly, due to various weather con-
ditions. As AT-110 calculates the altitude from the atmospheric pres-
sure, it is necessary to correct the current altitude in order to get more
precise data. It is recommended to make corrections whenever a reli-
able index (such as topographical map or altitude marker is available.
* The basic knowledge of the altitudes of your home, public facilities,
etc. will be useful information for correction.
How to Correct the Altitude
First, display the Main Screen. Then press the Set button, and the
altitude digits flash. To increase the figure, press the S/S button; to
decrease, press the Mode button. To increase/decrease rapidly, hold
down the button. Adjust the figure to the correct altitude, and press the
Set button to complete this operation.
Resetting Standard Atmospheric Scale
After adjusting the altitude to compensate for changes in weather, it may
be helpful to reset the AT-110 to it’s preset standard scale. In the Main
Screen, press the Mode button and the Set button simultaneously.
This resets the AT-110 to Standard Atmosphere (ISO 2533).
BASIC KNOWLEDGE OF ALTITUDE MEASURING
1. Altitude Measuring of AT-110
The AT-110 contains a highly sensitive atmospheric pressure sensor. It
estimates the altitude by using the “correlation between altitude and pres-
sure” based on the Standard Atmosphere (ISO 2533) of ICAO (Interna-
tional Civil Aviation Organization). Conventional pressure sensors are
affected by temperature and will therefore give errors. The AT-110 is
temperature-compensated every 20 seconds and records in 1 meter or
5 feet resolution. Also, it offers three types of measuring modes; Hike,
Ski and Fly; to give essential altitude data for various sports.
Note: The current altitude data may give an incorrect value tempo-
rarily, such as when it is taken out of doors from inside a building.
These temporary incorrect readings are to be expected and are not a
malfunction. Correct readings will return shortly.
2. The Correlation Between Altitude and Pressure
The higher the altitude gets, the lower the pressure becomes.
At venues of which altitudes are under 500 meters, the pressure de-
creases by approx. 12hPa per each 100 meters.
3. Weather and Atmospheric Pressure
Changes in weather from a high pressure system (clearer, calmer
weather) to a low pressure system (overcast, rain, storming weather)
can cause a change in the altitude reading of 100 meters, 325 feet or
more. Thunderstorms or other strong low pressure weather conditions
may cause even greater change. Even though the weather appears
stable, the pressure may considerably from morning to evening. Even in
seemingly stable weather, the morning to evening change can be as
much as 30 meters or 100 feet.
+
E
B
C
–
B
C
A.S.Level Pressure A.S.Level Pressure A.S.Level Pressure
4500 m 577 hPa 1000 m 899 hPa 300 m 978 hPa
4000 m 616 hPa 900 m 910 hPa 200 m 989 hPa
3500 m 658 hPa 800 m 921 hPa 100 m 1001 hPa
3000 m 701 hPa 700 m 932 hPa 0 m 1013 hPa
2500 m 749 hPa 600 m 943 hPa –100 m 1025 hPa
2000 m 795 hPa 500 m 955 hPa –200 m 1038 hPa
1500 m 845 hPa 400 m 966 hPa –300 m 1050 hPa
2000M
1000M
0M
A. S. Level
795hPa
899hPa
1013hPa
Pressure