Should you always cross-check altimeter readings with maps?

Importance of Verification

When relying on a handheld altimeter for navigation, it’s crucial to verify its readings against a map. Inaccurate altimeter readings can lead to navigation errors, especially in areas with complex terrain or multiple peaks. If the altimeter and map indicate a discrepancy of more than 100 feet, it’s best to recheck the setting and recalibrate the altimeter if necessary.

Understanding Altimeter Variability

Altimeter accuracy can vary depending on several factors, including atmospheric pressure, temperature, and altitude. In extreme weather conditions, an altimeter can deviate by up to 500 feet from the actual altitude. To minimize this variability, ensure the altimeter is adjusted to match the local atmospheric pressure, and use it in conjunction with a map and compass. For example, if the altimeter is set to match the pressure at sea level, it will be more accurate at higher elevations.

Practical Verification Techniques

To cross-check altimeter readings with a map, use the following techniques: (1) locate a known landmark or reference point on the map and verify its altitude using the altimeter; (2) use the map to calculate the expected altitude at a given location and compare it with the altimeter reading; (3) use the altimeter to track your ascent or descent and compare it with the map’s elevation profile. By combining these techniques, you can ensure that your altimeter readings are accurate and reliable, even in challenging navigation conditions.