ICOS data levels and quality

ICOS data are quantitative or qualitative attributes of variables or sets of variables that have been gathered using ICOS-recommended sensors at validated ICOS stations. The measurements are standardised due to protocols mutually agreed upon.

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ICOS data comply to international standards

ICOS management of data follows the international developments and standardisation. ICOS data and data that describes the datasets (metadata) are Findable, Accessible, Interoperable, and Reusable, so called FAIR principles. In practice, the FAIR principles aim at giving the user sufficient tools to understand the meaning of the data before and after downloading them.

We follow the standards of the Infrastructure for Spatial Information in Europe (INSPIRE), which are based on the ISO 19115 metadata standard.

Data product levels

ICOS Data Portal has three levels of data and data products: these are represented by the numbers 0, 1 and 2. In addition, there are elaborated data indicated as Level 3, that might be contributed, so non-ICOS, data.

Level 0 or Raw data

Raw data are information or objects directly obtained from human measurements or automated sensors that have not undergone any transformation. They may provide quantitative or qualitative information about physical variables of the environment and may be of various forms, such as images, text files or physical samples. Level 0 data are data in physical units either directly provided by instruments or converted from engineering units (for example, mV, mA, Ω) to physical units.

Level 1: intermediate observational data

These data are generated in intermediate steps in the data processing of Level 1 NRT or Level 2 data preparation, and for this reason they are not handled as persistent data and not shared outside the ICOS RI. The Level 1 data are used for internal quality checks,  for example in communication between Central Facilities and Principal Investigators. During the production of internal working data and following quality checks, important provenance information is generated that will be part of the provenance metadata of Level 2 data.

NRT data is a special type of Level 1 data that are  developed for fast distribution using only automated quality control within a certain short time interval (typically 24) hours of the measurement. NRT data are defined as a high-quality data set that will be distributed in the default way to the users. These data sets have their own provenance metadata that describe the raw data used, the versions of the software and the scripts, the settings and the results of the automatic quality control.

Level 2 data: final quality controlled observational data

Level 2 data are the main product of ICOS and form the final, quality-checked ICOS RI dataset, published by the Central Facilities, to be distributed through the Carbon Portal.

Level 3 data: elaborated products

All kinds of products elaborated by scientific communities that rely partly or completely on ICOS data products are called Level 3 data. The Carbon Portal will provide resources to integrate and disseminate Level 3 products, which will be provided on a voluntary basis by the research community and/or, if agreed upon, by collaborative projects. Data products that are based on ICOS observational data can be presented at the Data Portal as an elaborated product. In this case, please contact info (at) icos-cp.eu for more information.

Metadata: information on measurements methods & data processing

Dataset that describe the data are called metadata, and they are very important for the usability and transparency of data. Although not yet fully operational, the metadata for each dataset at ICOS Data Portal will give access to information on how the variables were measured and processed.

The ICOS measurements methods are described in protocols and various datasets are supported by specific documentation. Description of instruments and measurement protocols are available through the Thematic Centres.