Definition of Essential Geodetic Variables (EGVs)

Essential Geodetic Variables (EGVs) are observed variables that are crucial (essential) to characterizing the geodetic properties of the Earth and that are key to sustainable geodetic observations. Examples of EGVs might be the positions of reference objects (ground stations, radio sources), Earth orientation parameters, ground- and space-based gravity measurements, etc. Once a list of EGVs has been determined, requirements can be assigned to them. Examples of requirements might be accuracy, spatial and temporal resolution, latency, etc. These requirements on the EGVs can then be used to assign requirements to EGV-dependent products like the terrestrial and celestial reference frames. The EGV requirements can also be used to derive requirements on the systems that are used to observe the EGVs. During GGOS Days 2017 it was agreed that a Committee within the Bureau of Products and Standards would be established in order to define the list of Essential Geodetic Variables and to assign requirements to them. The Committee consists of representatives of the IAG Services, Commissions, Inter-Commission Committees, Projects, and GGOS Focus Areas.