Processing levels

Salle d'acquisition des données du sondeur multifaisceaux à bord de L'Atalante.

The data acquired by the French scientific community onboard oceanographic research vessels, as part of national or international programmes, are managed by SISMER, as the National Oceanographic Data Centre designated by France and the UNESCO's Intergovernmental Oceanographic Commission. The archiving of French data covers the fields of physical and chemical oceanography, geophysics measured en route and general information on the cruises and the collected datasets.

Different levels of data elaboration, determined by SISMER, can be distinguished by the processes applied.

Observation data: levels 0 to 3

Level 0

This so-called instrumental level corresponds to the raw data at full resolution emitted by the sensor. The data are time-ordered but are not always expressed in standardised units. This is why archiving at this level is neither systematic nor permanent.

Level 1

For this intermediate level, data are time-referenced and converted into units that comply with international standards. Instrumental specificities and errors may also be corrected. Recent instrumental systems directly provide data at this level.

Level 2

Level 2 data, at georeferenced geophysical level, are dated, spatially located and organised in a format that facilitates their scientific usage. Variations related to the acquisition conditions are also corrected and the data are thus expressed in a reference system that is independent of the measurement platform.

Level 3

Level 3 data are presented in relation to identical and standardised space-time reference scales. The data can thereby be easily compared and aggregated, including between different measurement programmes.

Products and synthesis: levels 4 and 5

These two levels include some interpretation of the information. From the products obtained, it is not possible to return to the lower level as the data resolution is generally reduced. The data are therefore archived independently.

Level 4

This level consists of interpolated data, resulting from data analysis.

Level 5

This level refers to synthesis products.