* Note that the following conditions will prevent you from obtaining accurate readings:
- When air pressure changes because of changes in the weather
- Extreme temperature changes
- When the watch itself is subjected to strong impact
There are two standard methods of expressing altitude: absolute altitude, which expresses an absolute height above sea level, and relative altitude, which expresses the difference between the altitudes of two different places. This watch expresses altitudes as relative altitude.
How the Altimeter Measures Altitude
The altimeter can measure altitude based on its own preset values (initial default method) or using a reference altitude specified by you.
When you measure altitude based on preset values
Data produced by the watch’s barometric pressure sensor is converted to approximate altitude based on ISA (International Standard Atmosphere) conversion values stored in watch memory.
When you measure altitude using a reference altitude specified by you
After you specify a reference altitude, the watch uses that value to convert barometric pressure readings to altitude (page E-44).
*When mountain climbing, you can specify a reference altitude value in accordance with a marker along the way or altitude information from a map. After that, the altitude readings produced by the watch will be more accurate than they would without a reference altitude value.
