An arbitrary tidal datum approximating the level of the mean of the lower low water at spring tides. It was first used in waters surrounding India.
Definition Source :
IHO Hydrographic Dictionary, English
Similarity to Source :
A tidal datum approximating the lowest water level observed at a place, originated by G.H. Darwin for the tides of India at a level below Mean Sea Level being equal to the sum of amplitudes of the harmonic constituents M2, S2, K1 and O1 usually below that of the lower low water at spring tides.
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