BPSGGOS Committee on

Essential Geodetic Variables (EGV)

Chair: Thomas Gruber (Germany)

The GGOS BPS Committee on Essential Geodetic Variables was established in 2018 in order to define a catalogue of Essential Geodetic Variables and to assign requirements to them. This Committee consists of representatives of the IAG Services, Commissions, Inter-Commission Committees, and the GGOS Focus Areas. 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 observing systems that are used to observe the EGVs. The EGVs can also serve as the basis for a gap analysis to identify observations needed to fully characterize the geodetic properties of the Earth.


The sequence of tasks to be performed by the Committee on Essential Geodetic Variables are to:

  • Identify the purpose of EGVs in context with Earth observation
  • Develop a concept and criteria on how to define EGVs
  • Prepare a roadmap document towards the definition of EGVs and initiate discussion among the committee and geodetic community
  • Define high level EGVs and prepare a classification scheme (matrix) linking them with geodetic products
  • Assign requirements for high level EGVs and analyse if existing geodetic products meet these requirements or identify needs
  • Discuss the purpose of and needs for lower level EGVs, e.g., as a tool to assess deployed and needed geodetic infrastructure.