The new quasi-geoid model IRQG09 for Iran

► Lateral density variation in the geoid can be reach up to decimeter level in Iran. ► Unification of height systems by normal height is useful for optimal adjustment of heights in Iran. ► Using of normal heights system is useful for tectonic deformation analysis. ► The least-squares modification of Stokes' formula gives the optimum results in quasi-geoid modelling in Iran.