Traditionally the height datum's of the countries has been derived from tide gauge observations. Nowadays due to scientific and technological developments reconsideration of the definition of height datum has become a must! Especially the removal of the country boarders (Unification of the Europe) and the inter-countries activities require unification of height datum's. In this paper we are aiming at a new method for unification and of height datums and sea surface topography (SST) computations. Our computation is based on (i) Tide gauge observations, (ii) Precise GPS observations at the tide gauge station, (iii) high degree/order spherical/ellipsoidal harmonic expansion. These observations are used according to following methodology:
(i) From tide gauge observations Mean Sea Level (MSL) is determined.
(ii) Using precise GPS observations and spherical/ellipsoidal harmonic potential at the level of MSL is computed.
(iii) The difference of the potential of MSL and geoids' potential value W0 is computed.
(iv) The computed potential difference is converted into height unit via nonlinear ellipsoidal/spherical Burns formula.
(v) The computed height difference in step (iv) is Sea Surface Topography (SST) at the tide gauge stations.
(vi) Knowing the SST at the reference tide gauge stations of various country, unification of height datum's can be performed.
As the case study SST at 4 tide gauge stations at main harbors of Iran along Persian Gulf and Oman Sea are computed. The theoretical details of the method and results the case study are presented.
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