Altitude

altitude, vertical distance of an object above some datum plane, such as mean sea level or a reference point on the earth's surface. It is usually measured by the reduction in atmospheric pressure with height, as shown on a barometer or altimeter. In surveying and astronomy, it is the vertical angle of an observed point, such as a star or planet, above the horizon plane. The altitude of a feature of the earth's surface is usually called its elevation. Recent spacecraft instrumentation has also measured vertical distances on the earth and other planets, determining the height of planetary features by means of radar and optical imaging.

In astronomy, altitude is the angular distance of a heavenly body above the astronomical horizon as determined by the angle which a line drawn from the eye of the observer to the heavenly body makes with the plane of the horizon. The reading of the apparent altitude, as determined by a telescope attached to a graduated circle, must be corrected for refraction by the atmosphere and for certain other effects to ascertain the true altitude. The altitude of the north celestial pole, which is approximately that of the star Polaris, is equal to the observer's latitude.

---

altitude

1. Geometry the perpendicular distance from the vertex to the base of a geometrical figure or solid

2. Astronomy navigation the angular distance of a celestial body from the horizon measured along the vertical circle passing through the body

---

altitude [′al·tə‚tüd]

Abbreviated alt.

(engineering)

Height, measured as distance along the extended earth's radius above a given datum, such as average sea level.

Angular displacement above the horizon measured by an altitude curve.

(mathematics)

The perpendicular distance from the base to the top (a vertex or parallel line) of a geometric figure such as a triangle or parallelogram.

---

Altitude 

the angular displacement of an observed object, such as a flight vehicle or a celestial body, above the celestial horizon. In astronomy, altitude is used together with azimuth to determine the direction to an object in the horizon system of coordinates.