A feasibility study on the unification of the Italian height systems using GNSS-leveling data and global satellite gravity models

Regional height systems are usually referred to the mean sea level at a reference tide gauge. As the mean sea level gravity potential changes from place to place, regional systems refer to different equipotential surfaces and the establishment of a unified datum requires the determination of one bias per region. This is what is referred to as the height datum problem. The possibility to solve this problem by exploiting the nowadays available satellite gravity mission data, the high resolution global gravity potential models, GNSS heights, as well as leveling and gravity data has been explored. A solution strategy and a first error budget have been presented in Gatti et al. (J Geod 87(1):15–22, 2012), showing that an accuracy of about 5 cm can be globally achieved in the bias computation. In the present work, this strategy, with refinements in the error modeling, is applied to the Italian case, where different height systems are used for the mainland and Sicily and Sardinia islands.