Altitude is a term used in geography to describe the height of an object or point above a specific reference level, usually the Earths surface or mean sea level. It is a distance measurement, usually in the vertical or "up" direction, between a reference datum and a point or object. Altitude is commonly expressed in meters or feet.

Altitude is often used interchangeably with the term elevation, but they have slightly different meanings. Elevation is the measurement of the height of a geographical feature that is above mean sea level (MSL) . Elevation uses a fixed reference point, mean sea level, from which these features are measured. Elevation measures the height of things that are on the ground.

In aviation, there are five types of altitude: indicated altitude, absolute altitude, true altitude, height, and pressure altitude. Indicated altitude is the altitude shown on the altimeter. Absolute altitude is the altitude in terms of the distance above the ground directly below. True altitude is the altitude in terms of elevation above sea level. Height is the vertical distance above a certain point. Pressure altitude is the air pressure in terms of altitude in the International Standard Atmosphere.

Altitude is an important concept in geography as it helps in understanding the topography, climate, and ecology of a region. It is also used in aviation and space sciences to describe the vertical distance or height of an object or point above a specific reference level.