Does humidity impact the performance of barometric altimeters?

Temperature and Humidity Effects

Barometric altimeters rely on the principle that air pressure decreases with altitude. However, temperature and humidity can significantly affect air density, making it challenging for the altimeter to accurately determine altitude. A change of 1°C in temperature can cause a 3% change in air pressure, while a 10% change in humidity can lead to a 1% change in air pressure. To minimize the impact of humidity, it’s essential to calibrate the altimeter in stable, dry environments.

Altitude Calibration Techniques

To improve the accuracy of barometric altimeters, pilots and navigators often use altitude calibration techniques. One method involves setting the altimeter to the local QNH (mean sea-level pressure) at sea level or a nearby reference point. Another method involves using a known altitude reference point, such as a mountain peak, to establish a baseline for altitude corrections. By applying these calibration techniques, navigators can reduce the impact of humidity on altimeter performance and achieve more accurate altitude readings.

Altitude Compensation Methods

In addition to calibration techniques, navigators can use altitude compensation methods to account for humidity-induced variations in air pressure. One method involves using an aneroid barometer, which measures altitude by comparing the pressure difference between two points. Another method involves using a GPS device, which can provide accurate altitude readings and be used to correct altimeter readings. By combining these methods, navigators can achieve accurate altitude readings, even in challenging environments with high humidity.