Hypsography

Hypsography studies the distribution of elevations on the surface of the Earth, and is sometimes applied to other rocky planets such as Mars or Venus. The term originates from the Greek word "hypsos" meaning height. Most often it is used only in reference to elevation of land but a complete description of Earth's solid surface requires a description of the seafloor as well. Related to the term hypsometry, the measurement of these elevations of a planet's solid surface are taken relative to mean datum, except for Earth which is usually taken relative to the mean sea level.