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, mean-tide system is for handling permanent tide. Second, reference level of height defined equipotential surface where geopotential has a conventional value W0=62636853.4 m2s-2. This was first determined empirically to provide good approximation global mean sea and then as convention. I analyse tidal aspects based on W0. W0 definition independent surface, but different systems, functions are involved W equation W=W0. find that empirical determination estimate inconsistent from viewpoint systems. However, consistent same data round off value. propose simplified IHRF numbers would make it possible transform between zero-tide using simple datum-difference surface. should adopt (best) potential such contained IERS Conventions use basis other formulas. tide-free coordinates ITRF, Global Geopotential Models central modelling purposes IHRF. present set correction formulas can be used move model before, middle, or after processing, finally To reduce confusion around multitude systems primarily done system, with an add-on.