altimetri

Altimetri are devices that measure altitude, or height, relative to a defined reference surface. In aviation, the most common type is the barometric altimeter, which infers altitude from ambient air pressure using a model of the standard atmosphere. Depending on how the device is set, it can indicate altitude above mean sea level (QNH), above a specific airfield (QFE), or above the standard sea level pressure (QNE). Barometric altimeters are sensitive to weather and temperature and require regular calibration to maintain accuracy.

Beyond barometric instruments, other important types include radio altimeters, which measure the distance from an aircraft to the ground by timing reflected radio waves; laser or lidar altimeters, which use laser pulses to determine precise distances to terrain or surfaces; and satellite-based altimetry, which uses radar or laser across the ocean and land to map surface heights on a large scale. Each method relies on different physical principles and serves different applications, from aviation safety to geodesy and Earth observation.

Applications of altimetri span several fields. In aviation, they support altitude control, terrain awareness, and obstacle clearance. In surveying and cartography, they contribute to elevation models and topographic maps. Oceanography and geodesy use satellite altimetry to monitor sea-surface height, ocean circulation, and land elevations. In engineering and robotics, altimeters enable terrain-following and precise height measurements for autonomous systems.

Common considerations include reference frames and units (meters or feet), calibration and reference pressure settings, and sources of error such as atmospheric conditions, instrument drift, and terrain-induced reflections.