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As average sea levels rise, will contour lines and spot heights on maps need to be recalculated? If so, when?
Simon Ritchie
Leatherhead, Surrey, UK
Height above mean sea level is only one of at least three measures of height. Two others are the height above a perfect ellipsoid that approximates the shape of Earth, and the height above an irregular shape called the geoid, which is another useful approximation of our planet’s shape. Modern GPS-based surveying equipment gives your position relative to Earth’s centre of mass. That is most sensibly expressed as geoidal or ellipsoidal height or both.
The…
