BathyElli v2.1 HZ surface

The BathyElli v2.1 HZ surface is a realisation of the ellipsoidal height of the Hydrographic Zero (Chart Datum). The Hydrographic Zero realised by the BathyElli v2.1 HZ surface is expressed at the reference date of 2000/01/01. The evolution of the realisation of the Hydrographic Zero by the BathyElli v2.1 HZ surface is less than 3 mm/year in absolute value. For applications that do not require an uncertainty better than a few centimetres on the vertical, no change of epoch is necessary. The Hydrographic Zero realised by the BathyElli v2.1 HZ surface is expressed by its ellipsoidal height in the legal geodetic datum according to the decrees n°2000-1276 and 2006-272. For metropolitan France, the legal geodetic datum is RGF93 v2 and the associated ellipsoid GRS80. The difference between RGF93 v2 and the latest realisation of ITRS or the latest realisation of WGS84 is less than a few meters. For applications that do not require an uncertainty of better than a few metres on the horizontal, no change of realisation of the geodetic system is necessary. This product covers the intersection between the Shom tidal model and the different tidal zones of metropolitan France.