QA4EO is a best practice framework endorsed by The Group on Earth Observations (GEO) to establish The Global Earth Observation System of Systems — based on coordinated and harmonised processes and activities that enable interoperability. Its internationally agreed principles contain a suite of guidelines that provide a consistent approach across disciplines, including for fundamental data records (FDRs), thematic data products (TDPs), and fiducial reference measurements (FRMs).


It is critical that data and derived products are easily accessible in an open manner and have associated with them an indicator of quality traceable to reference standards (preferably SI) so users can assess suitability for their applications, i.e. the ‘fitness for purpose’.


A QI shall be based on documented and quantifiable assessments of evidence demonstrating the level of traceability to internationally agreed (where possible SI) reference standards.

Quality Indicators

A Quality Indicator (QI) shall provide sufficient information to allow all users to readily evaluate the fitness for purpose of Earth observation data or derived products.

Getting started

Formal QA4EO Guidance documents have been supplemented by more recent guidance, produced through the work of several collaborative research projects between metrology institutes and Earth observation practitioners.

To get started, follow these suggested steps ...

The Quality Assurance Framework for Earth Observation (QA4EO) was established and endorsed by the Committee on Earth Observation Satellites (CEOS) to meet a requirement identified by the Group on Earth Observations (GEO) to enable interoperability and quality assessment of earth observation data.

This website and the metrological principles documents it hosts were developed in the frame of the Instrument Data Quality Evaluation and Assessment Service - Quality Assurance for Earth Observation (IDEAS-QA4EO) contract funded by ESA-ESRIN (n. 4000128960/19/I-NS), and builds on the work of previous projects, see Acknowledgements.

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