Why do watches have errors when measuring air pressure?

In some extreme environments, the watch may have problems measuring air pressure.

In a low pressure environment, the altimeter may not be able to provide accurate altitude measurement data.

Altitude data will deviate under abnormal weather, and the error will be very large.

As we all know, atmospheric pressure not only changes with altitude, but also changes in weather, sunshine, earthquakes, etc. This also causes errors in altitude measurement. So frankly speaking, any watch that does not use GPS to measure absolute altitude is deceptive and has no practical meaning. It is generally only used to measure relative height changes in a short period of time. Please refer to the watch manual for specific operations. Because when the relative altitude changes, only the altitude affects the air pressure, and the impact of weather and other factors is minimal, so it can be measured quickly and accurately. This is why aircraft calibrate the barometer and altimeter when landing before using it.

Altitude measurement is done by measuring air pressure and converting it into an altitude value. The premise for correct use of altitude measurement is that the weather remains unchanged in the short term, but if the altitude changes, then the change in air pressure can be considered to be caused by the altitude change, so the corresponding altitude change value can be calculated. Note that the emphasis here is on short-term weather invariance, and the result of altitude measurement is relative altitude.

Therefore, the correct usage of the altimeter is as follows:

Before starting to climb, first correct the altitude value. There are two situations here.

A. If you know the altitude at the foot of the mountain, for example by finding a stone marker or having a local map with contours (such as a military map), you can enter the local altitude into the table as an altitude reference. In this way, during the mountaineering process, what is displayed on the table is the altitude value of the passing location.

B. If you do not know the altitude at the foot of the mountain, you can set the altitude reference value to 0. In this way, during the mountain climbing process, what is displayed on the table is the height of the passing location relative to the foot of the mountain.