Setting the altimeter correctly will tell you your true altitude, in other words your altitude above sea level. [1] X Research source The altimeter setting is displayed in a window on the altimeter called the Kollsman window. Your altimeter will have an adjustment knob to adjust the reference pressure and change the numbers displayed in this window. [2] X Research source
For example, when the pointer is between the 0 and the 1, then you have not reached 10,000 feet of altitude yet and you would read your altitude from the other pointers. If the pointer is exactly on the 1 then you are at exactly 10,000 feet. When the 10,000-foot pointer is past the 1 on the dial but not yet at the 2, then you would read it as 10,000+ and proceed to read the next pointers to get your exact altitude. Note that in aviation, the standard unit for measurement for altitude is in feet, so you would not be reading an altimeter in meters.
For instance, if the 1000-foot pointer is exactly at the 2 on the dial, and the 10,000-foot pointer was between the 0 and the 1, then your altitude is 2000 feet. If the 1000-foot pointer is past the 1 but not at the 2 yet, then you read it as 1000+ and move on to reading the 100-foot pointer to get the precise altitude.
For example, if the 100-foot pointer is at the 2nd line past the 5, then you read it as 540 feet. Say that the 10,000-foot pointer was at the 1, the 1000-foot pointer was at the 2, and the 100-foot pointer is at the 3rd line past the 6. You would read the total altitude as 10,000+2,000+660=12,660. You are flying at 12,660 feet above sea level.
For example, if the drum reads 6000, and the pointer is at the 2nd line past the 2, then you would read it as 6000+200+40=6240. Your altitude is 6240 feet.
It’s important to note that absolute altitude is different from true altitude. True altitude tells you how high you are above sea level based on air pressure, while absolute altitude tells you how high you are above the nearest terrain below you using radar.
Refer to the instructions for your altimeter watch if you aren’t sure how to set the altitude. You need to calibrate your altimeter watch with known altitudes regularly to keep the readings accurate. For example, if you are hiking or mountain climbing, keep an eye out for signs that state your current altitude and set your altimeter watch to match.
Most modern altimeter watches display elevation in increments of 3 ft (0. 91 m). [9] X Research source
If the elevation on your watch is rising but you are not climbing in elevation, then it’s possible that a storm is coming. When the altitude on your watch is falling and you are not descending in elevation, then it could indicate that the weather is clearing up. It’s important to understand that because altimeter watches are affected by changes in air pressure due to both actual elevation and weather, the reading on your watch is always an estimate. This is why it’s crucial to always calibrate your watch whenever you know your elevation to get the most accurate reading.
