Dynamic height
Dynamic height (symbol H d {\displaystyle H^{\text{d}}} or H dyn {\displaystyle H^{\text{dyn}}} ) is a way of specifying the vertical position of a point above a vertical datum; it is an alternative for orthometric height or normal height. It can be computed (in SI units of metre) by dividing the location's geopotential number (symbol C, in square metre per square second) by the normal gravity (symbol gc, in metres per square second) at 45 degree latitude and zero height, a constant value (9.806199203 m/s2): H d = C / g c {\displaystyle H^{\text{d}}=C/g_{c}} Dynamic heights are usually chosen so that zero corresponds to the geoid.