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.

About QA4EO

The Quality Assurance framework for Earth Observation (QA4EO) was established and endorsed by the Committee on Earth Observation Satellites (CEOS) as a contribution to facilitate the Group on Earth Observations (GEO) vision for a Global Earth Observation System of Systems (GEOSS), which requires the interoperability and quality assessment of earth observation data.

QA4EO encompasses a framework and set of ten best-practice guidelines, with example templates to aid consistent implementation with the necessary evidence of compliance, thereby allowing data product users to assess adequacy and 'fitness for purpose' of datasets.

QA4EO-compliant processes unequivocally assure data quality and encourage harmonisation across the whole GEO community, providing an internationally-coordinated operational framework to facilitate interoperability and harmonisation. Although the QA4EO guidelines were originally developed to meet the needs of the space community, they have been written with the aid of national metrology institutes of the UK and the USA and, where appropriate, are based on best practices of the wider non-EO community. They should therefore be readily adoptable by all GEO communities as a top-level framework that can subsequently be translated and implemented to serve each specialist need.

QA4EO is driven by the key principle that all measurements/processes must have associated quality indicators (QIs) based on documented evidence of traceability to reference standards agreed by the scientific community.

QA4EO, therefore, requires the establishment of an unbroken chain of uncertainty evaluation from the platform and on-board payload elements to the final product processing steps, integrating the supportive ground-based activities.

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.

The National Physical Laboratory is committed to protecting and respecting your privacy. See privacy statement.