Volta
The permanent tide and the International Height Reference Frame IHRF
The International Height Reference System (IHRS) adopted by the IAG in 2015 contains two novelties. First, the mean-tide system is adopted for handling the permanent tide. Second, the reference level of height system is defined by the equipotential surface where the geopotential has a conventional value W0=62636853.4 m2s-2. This value was first determined empirically to provide a good approximation to the global mean sea level and then adopted as a reference value by convention. I analyse the tidal aspects of the reference level based on W0. The W0 is by definition independent of the tidal system adopted for the equipotential surface, but for different tidal systems, different functions are involved in the W of the equation W=W0. I find that …