Zero level

This article covers the importance of zero level in geography. For the physical term see zero level (physics)

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The zero level is an area to which the height zero is assigned.

earth

On Earth, the zero levels for reference altitudes are often defined based on a sea ​​level . Depending on the height definition , this surface corresponds to an ellipsoid of revolution , geoid , quasigeoid or another irregular surface.

→ Main article : Height above sea level

Other planets

For planets with a solid surface , the zero level is the surface of the ellipsoid of revolution of equal volume.

On planets without a solid surface ( gas planets ) it is the level at which the gas pressure is 1  bar . This definition is based on the conditions on earth, where at zero level (sea level) the average atmospheric pressure is 1.013 bar.