Altimeters
How does an altimeter work But how can an altimeter measure elevation? Air pressure decreases at a predictable rate with an increase in altitude, so an altimeter shows air pressure on a scale calibrated in feet or meters above or below the sea level. Therefore, an altimeter is basically a modified barometer. Accuracy depends on the weather If the air pressure depends on the weather, then the accuracy of an altimeter depends on the weather. Changes in weather could easily decrease the precision more than 10 times, even for high quality altimeters. Note that during apparently stable weather conditions, your indicated elevation may change. Calibrate as often as possible An altimeter can be of good navigation help if you use it right. But don't trust the instrument until you first set it at a known elevation. Then, check the reading whenever you reach another point of known elevation, so you can reset it if necessary. It is recommended that every time you use an altimeter, it be recalibrated to achieve the highest altitude accuracy reading. to: "Portable navigation system" Back to: Wilderness backpacking homepage
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