Essential Geodetic Variables (EGV) Data Levels and Supply Chain Tiers

Data Levels (Data State)

This table summarises the data levels for EGVs as formalised in the GGOS EGV White Paper V7.0 (January 2026). Each level represents a distinct state of the data as it progresses through the geodetic supply chain.

Level	Name	Description	Purpose / Applicability
Basis	Basis Variables	Geodetic observing infrastructure and the standards and conventions required to produce higher-level EGVs. Includes physical station networks, space segments, numerical standards, and background models.	Foundation for all EGV production. Not itself an observed or derived variable, but a prerequisite for the entire supply chain. The two Basis EGVs are: Geodetic Infrastructure and Geodetic Standards and Conventions.
Level 1	Level 1 Variables	Data collected by satellites, airborne, or ground-based infrastructure annotated with geo-location and epoch, based on agreed standards and conventions.	Input for determination of Level 2 and Level 3 EGVs. Data formatted to agreed community standards (e.g., RINEX for GNSS, SINEX for combined solutions). The formal Level 1 EGV is Geodetic Observations — recognising that technique-specific observations (VLBI, SLR, GNSS, DORIS) are themselves essential variables.
Level 2	Level 2 Variables	Products determined from a combination of various Earth observation datasets, describing specific parameters of the Earth system in space and time domains.	Four EGVs are defined at this level: Satellite Orbits, Station Positions and Variations, Sea Water Level Records, and Land and Marine Gravity Data. These serve as primary inputs to Level 3 products.
Level 3	Level 3 Variables	High-level accumulated products describing the geometric and physical shape of the Earth or its orientation in space, after significant data processing and/or combination.	Fourteen EGVs are defined at this level across Global, Land, and Ocean domains. Application-oriented and directly applicable to multidisciplinary Earth system monitoring; the primary products consumed by downstream science and policy users.

Source: Gruber, T.; Angermann, D.; Sánchez, L. (2026), Definition of Essential Geodetic Variables (EGV): Contribution of Geodesy to Earth Observation, White Paper Version 7.0, GGOS, January 2026. Pages 5–10.

Note on V7.0 changes from V6.0: V7.0 introduced two structural changes. First, what was "Level 0" is now designated Basis to better reflect its role as infrastructure and standards rather than an observational data state. Second, a new Level 1 EGV (Geodetic Observations) has been formally defined. The total EGV count increases from ~18 (V6.0) to 21 EGVs in V7.0, with the addition of Regional Reference Frames and Regional Gravity Field Model at Level 3.

For the full EGV inventory and product mapping, see EGV_Product_Mapping.md.

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Supply Chain Tiers (Infrastructure & Process)

While "Levels" describe the state of the data itself, "Tiers" are an architectural mapping framework used in this project to categorise the organisations, processes, and infrastructure that move data through the supply chain. The Tier framework is a supply chain analysis construct developed for this project; it is not defined in the GGOS EGV White Paper.

Tier	Name	EGV Data Level	Description	Typical Actors
Tier 0	Data Acquisition & Telemetry	Basis	Physical observation, instrument calibration, and first-mile data transmission. The infrastructure at this tier corresponds to the Basis EGVs: Geodetic Infrastructure and Geodetic Standards and Conventions.	Observatories, Ground Tracking Stations, Operational Data Centres (ODCs)
Tier 1	Global Archiving	Level 1	Ingestion to agreed standards (e.g., RINEX, SINEX), long-term preservation, and synchronised data mirroring across global and regional centres. Outputs correspond to the Level 1 EGV: Geodetic Observations.	Regional Data Centres (RDCs), Global Data Centres (GDCs)
Tier 2	Analysis & Processing	Level 1 → Level 2 (intermediate)	Independent mathematical processing of archived Level 1 data into individual solutions. Outputs are more than raw data but are not yet the authoritative EGV product — they become Level 2 only after Tier 3 combination.	Analysis Centres (ACs), Academic Institutions, Space Agencies
Tier 3	Combination	Level 2 or Level 3 EGV	Mathematical integration of independent Analysis Centre solutions into the authoritative, official EGV product. For GNSS Orbits and Land/Marine Gravity Data, the output is a Level 2 EGV; for Global Reference Frames and Earth Orientation Parameters, it is a Level 3 EGV.	Analysis Centre Coordinators (ACCs), Combination Engines (e.g., SPOCC/GFZ), ITRS Product Centres
Tier 4	Validation & Distribution	Level 2–3 EGV (published)	Independent quality assurance, product validation against standards, and global distribution of the authoritative EGV products.	Validation Services (e.g., IERS), IGS product broadcasters, global data archives (CDDIS, IGN)

For detailed mapping of EGV Data Levels onto specific supply chain tiers — including latency classes and workflow annotations — see the EGV Data Level Progression Through the Supply Chain section in EGV_Product_Mapping.md.

For risk classification methodology applied at each tier, see mathmatical_rubric.md.