A measurement indicating the vertical distance from the average level of the ocean to a specific point on land, often used to describe the altitude of terrain or the elevation at which aircraft operate.

The standardized reference point for gauging the height of geographical features, where the average sea level in Tokyo Bay serves as the zero baseline for determining altitude.

The elevation of land or structures, calculated from the average height of the sea, which is important for understanding geographic and environmental conditions, particularly in relation to flooding risks and climate factors.