# altitude

1. Altitude in astronomy is the angular distance
of a celestial body above or below the observer's horizon,
measured vertically. Altitude is 0° at the horizon and 90° at
the zenith. It is specified together
with azimuth to give the horizontal
coordinates of an object.

2. Altitude in aerospace is the vertical distance
of an object above the observer. The observer may be anywhere on Earth
or at any point in the atmosphere. Absolute altitude is the vertical
distance to the object from an observation point on Earth's (or some
other body's) surface.

3. Altitude in mathematics is the perpendicular
line segment from one vertex of a figure
or solid to an edge or face opposite to that vertex. Also the length
of such a line segment.