What is one of the primary functions of an altimeter?

An altimeter is primarily designed to indicate the aircraft's altitude by measuring the atmospheric pressure. As an aircraft ascends or descends, the surrounding air pressure changes, which the altimeter detects. This pressure change is converted into altitude readings, allowing pilots to determine their height above sea level or above ground level.

Wind speed is a measurement of how fast the air is moving, which is not a function of an altimeter. Air density, while related to altitude, is not directly measured by an altimeter itself; instead, it is influenced by altitude. Navigation information typically comes from instruments like the compass or GPS, rather than an altimeter. Thus, the primary function remains clearly focused on altitude indication.