Elevation

Elevation is the vertical height of a place above a chosen reference surface, commonly mean sea level. Its value depends on the reference datum and measurement method.

Vertical datum: A reference surface used to define elevations and depths. It specifies the zero surface from which an elevation is measured.
Leveling: A surveying method that determines height differences using horizontal sight lines and graduated staffs. It transfers elevation from a known benchmark across the ground.
Topographic map: A map that represents Earth's terrain and surface features, often using contour lines. It communicates elevation and landform shape across a region.
Environmental lapse rate: The rate at which the surrounding atmosphere's temperature changes with altitude at a given time and place. Air temperature commonly decreases with increasing elevation, shaping local conditions.
Mean sea level: The average sea-surface height over a specified period, used as a practical reference level. It is a common reference for reporting land elevations.
Global Navigation Satellite System: A satellite-based system that determines positions on Earth using signals from orbiting navigation satellites. GNSS provides position data that can be converted to elevation with a suitable datum model.
Hypsometry: The measurement and analysis of the distribution of elevations across land or a planetary surface. It summarizes how much land lies at different elevations.
Orographic lift: The upward movement of air forced by terrain, often producing clouds and precipitation on windward slopes. Elevated terrain redirects airflow and creates strong regional rainfall contrasts.
Geoid: An Earth-shaped equipotential surface approximating global mean sea level and extended beneath continents. It provides a gravity-based reference surface for heights.
Digital elevation model: A digital representation of ground-surface elevations arranged as a grid or other spatial data structure. It stores elevation values across an area for mapping and analysis.

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