GMES Land Quality Assurance Approach

The main goal of any quality assurance (QA) concept is to validate and ensure the agreed quality of a product. Thus, it is important to produce reproducible and traceable results. Therefore, quality assurance not only guarantees quality, but also helps to streamline production (reduction of cost) and provide comparable products across different production sites and service regions.

GMES land related services produce a number of thematic mapping products derived from remote sensing data as a basis for downstream products, such as model results addressing water quality, land consumption, quality of life etc. Hence, it is of great importance that the satellite based land information is of high quality and that the derived mapping products can be trusted.

Standards & Schemes

The quality assurance approach of GSE Land Information Services builds on three pillars

• product and service standards jointly set-up and agreed among user organisations and formalised with service providers. This includes standardised product descriptions and interpretation guidelines applicable to all European conditions.

• a qualification scheme accepted by users organisations and service providers, defined by scientific experts representing demand and supply including scientific and engineering know-how.

• an implementation scheme for the qualification elements performed by independent auditors and supervisors:

• The TÜV for independent service chain audits and training of internal auditor's, (audit philosophy and method)

• A trusted European expert on land cover / land use mapping acting as supervisor for chief interpreters in the production units

• An independent central technical reference team led by the ETC -TE (comparable to CLC 2000 core team established at the ETC -TE or MARS team established at JRC AgriFish Unit) who is responsible for the quality assurance process and the quality control of the final land cover products

Validation

The main step of the quality assurance approach is the validation of the product. It includes three main components:

• qualitative verification by the QA technical team in which some intermediate results of the service provider interpretation will be commented by the QA team and potential deviations from the specifications will be highlighted. The verification will be done during the course of production and is meant to increase data quality.

• A quantitative validation : The QA team will perform an independent external technical quality control after the finalisation of the mapping product to check whether the products reached the desired quality. It is based on a sampling scheme that takes care of statistical representativeness of the samples together with an acceptable cost ratio with regard to the required independent reference data in a European-wide context. The validation is carried out in a “blind” approach by experienced interpreters without knowing the interpretation done by the service provider. Then, this information is compared to the mapping results from the service providers and statistical indicators are computed such as overall accuracy, user and producer accuracy and Khappa coefficients based on the error matrices produced

• Requisites validation : the user will validate the product if it fulfils the needs that the user itself has included in the product requisites. The figure below illustrates the validation process.

Please view the specific sections in the Validation Protocol which describes in detail the Quality Assurance approach of GSE Land and the Validation Reports which provides for each mapping service delivered the status achieved so far.