| Term: | Altitude |
| Definition: |
The vertical distance of a point above a datum. The vertical datum is usually an estimate of mean sea level. Older measurements were often determined in a local coordinate system and were not tied to a global reference frame. Some were made not with surveying instruments but with barometers, in reliance on the decrease of atmospheric pressure with altitude. It is now usual to measure altitude or elevation using the Global Positioning System or an equivalent global navigation satellite system. Altitude and elevation are synonyms in common usage, although altitude is less ambiguous. The unqualified word 'elevation' can also refer, for example, to the act of elevating or to angular distance above a horizontal plane. IHPGlacierMassBalance
Vertical distance of a level, a point or an object considered as a point, measured from mean sea level. (TR) WMOHydrology A measure (or condition) of height, especially of great height, as a mountain top or aircraft flight level. In meteorology, altitude is used almost exclusively with respect to the height of an airborne object above the earth's surface, above a constant-pressure surface, or above mean sea level. The measurement of altitude is accomplished by altimeters in aeronautics, and the entire study is called altimetry. AMSglossary Vertical distance above sea-level. PhysicalGeography GCW |