A fundamental development of the next coming years shall be the definition and the implementation of a high-accuracy and space-time continuous observation system for monitoring Earth\u2019s surface deformation. The IAG project GGOS (Global Geodetic Observing System) will be the geodetic contribution to such a realization. A detailed knowledge of the crustal deformation is a key element to achieve a thorough comprehension of how the solid Earth responds to deformational forces and for an improved understanding of the seismogenetic cycle. We have studied and applied a combined observational strategy for monitoring and reliably identifying both seasonal and log-term crustal movements, namely height variations/changes. The strategy adopted is based on a multidisciplinary approach that combines the information provided by GPS, InSAR and terrestrial gravimetry. The results of these different techniques are compared and combined in a study on land subsidence in the southeastern Po Plain and the northern Adriatic coast, in Italy
