A method for computing offset of zero points of height datums with respect to geoid


Department of Surveying and Geomatics Engineering, University of Tehran, P.O. Box 11365-4563


In this paper a method for computing offset of zero points of height data with respect to geoid by solving a fixed-free two-boundary value problem (FFTBVP) is addressed. Application of the following observables in the FFTBVP by presenting their corresponding integral equations and the computational algorithm is fully covered.
a) Gravitational: gravity potential, modulus of gravity vector, astronomical latitude and astronomical longitude.
b) Satellite altimetry.
The method presented is applied to compute the offset of zero point of Iranian height datum with respect to geoid. According to the results, height datum of Iran is 0.094 m below the geoid.  In this method since the offset of zero points of height data are determined with respect to geoid, height datum unification can be achieved by repeating the same procedure at in different countries.
The recommended boundary value problem has the capability of incorporating any type of observations which contain information about the gravity field of the Earth in a simultaneous gravity field modeling, therefore the method by taking advantage of all existing gravity observables can provide the optimum solution for obtaining the offset of the zero points of the height data and/or height datum unification.