Altitude is the elevation of an object from a known level or datum, called zero level. Most often this level is defined as the absolute sea level, but it can vary.
In aviation, the term altitude is used to describe elevation above mean sea level, the term height refers to elevation above a ground reference point and the term flight level is the elevation according to a standard pressure altimeter setting.
Atmospheric pressure decreases with altitude.
In North America and the UK altitude is usually measured in feet. In continental Europe and other parts of the world altitude is measured in metres.
- High altitude = 1500m – 3500m
- Very High altitude = 3500m – 5500m
- Extreme altitude = 5500m – above
- 19 September, 1783 — 500m (1,700ft) animal carrying Montgolfier hot-air balloon.
- 15 October, 1783 — 26m (84ft) Pilātre de Rozier in a Montgolfier tethered balloon.
- 1 December, 1783 — 2.7km Professor Charles and assistant Robert in Charliere, his hydrogen-filled balloon.
- 1784 — 4km Pilātre de Rozier and the chemist Proust in a Montgolfier.
- 18 July, 1803 — 7.28km Etienne Gaspar Robertson and Lhoest in a balloon.
- 1839 — 7.9km Charles Green and Spencer Rush in a free balloon.
- 5 September, 1862 — 9km Coxwell and English physicist Glaisher in a balloon.
- 4 December, 1894 — 9.155km German meteorologist Berson in an airship.
- 31 July, 1901 — 10.8km German meteorologist Berson and Süring in a free balloon.
In astronomy and surveying, altitude is one of the two coordinates of the horizontal coordinate system, and refers to the vertical angle from the horizon. The other coordinate is azimuth, which refers to the horizontal angle from the north.
In geometry, an altitude of a triangle is a line passing through one vertex and being perpendicular to the opposite side. See altitude (triangle).