On Geoid

The classic geoid is defined as an equigeopotential surface,a part of which coincides with the static sea level,and the latter is commonly replaced by the mean sea level.Unfortunately,the mean sea level is not an equigeopotential surface.If the accuracy requirement is higher than 10 cm,the above classic definition is no longer suitable.The modern definition of the geoid is as follows:the geoid is such an equigeopotential surface that is nearest to the mean sea level.However,the key problem is how to determine the geoid.To determine the geoid,one should determine both its shape and the geodetic potential constant W₀.