Quick Answer
Air pressure readings are affected by altitude, with higher altitudes resulting in lower air pressure. For every 1,000 feet increase in altitude, air pressure decreases by about 0.87 psi, which can significantly impact navigation altimeter readings.
Understanding Altitude and Air Pressure
When using a navigation altimeter, it’s essential to understand how altitude affects air pressure readings. At sea level, air pressure is approximately 30.08 inches of mercury (inHg). As altitude increases, air pressure decreases. For example, at 5,000 feet, air pressure is around 20.5 inHg, and at 10,000 feet, it’s approximately 17.2 inHg. This decrease in air pressure can cause the altimeter to display incorrect readings.
Correcting for Altitude with Altimeter Settings
To accurately navigate with an altimeter, it’s crucial to set the device to the current altitude or adjust for the local pressure setting. This can be done by consulting a barometric pressure chart or using a Kollsman window, which is a built-in pressure-setting device found on many altimeters. The Kollsman window allows the user to adjust the altimeter reading by setting the current pressure, which can be determined by consulting a pressure chart or using a portable aneroid barometer. By setting the altimeter correctly, users can ensure accurate altitude readings and avoid navigation errors.
Practical Considerations for Survival Situations
In a survival situation, altitude and air pressure can have significant consequences. For example, at high altitudes, the lower air pressure can cause hypoxia, leading to decreased cognitive function, fatigue, and increased risk of altitude sickness. Additionally, accurate navigation is critical for finding shelter, water, and food, making correct altimeter settings essential for survival. By understanding how altitude affects air pressure and using the Kollsman window or pressure charts, users can ensure accurate navigation and stay safe in the wilderness.
Find more answers
Browse the full Q&A library by topic, or jump back to the topic this question belongs to.