Quality Control
In the construction of ESEAS standard, it was recognised that a common set of procedures should be adopted for the quality-control of tide gauge data. To a great extent, these procedures can be adopted from those specified by the Intergovernmental Oceanographic Commission (IOC) for the Global Sea Level Observing System (GLOSS), although it is reasonable to expect that a review of methods should be undertaken for European applications. The procedures include checking for unexpected anomalies in the time series, or in the derived tidal parameters, and in the filtering of the raw data to provide monthly mean values (which are submitted to the Permanent Service for Mean Sea Level (PSMSL) which forms the basis of most climate-change related studies of sea level variations).
Quality control extends to other factors. The documentation of datum information (relationship of the recorded sea levels to the level of benchmarks on land) is essential. Diagrams, maps and other metadata also have to be provided. However, there is at present little standardisation of methods for consolidating and archiving such information.
Quality control is also related to issues such as the availability of data in real-time. If data are inspected every day or, in advanced systems, if data can be flagged for errors by automatic software, then faults can be rapidly attended to and fixed. This contrasts with the traditional form of sea level recording on paper charts, where errors are detected a considerable time after they occur.
Application of standardised sea level quality control, and agreed filtering techniques will ensure that data supplied to the global sea level databanks (e.g. PSMSL and IHO) are consistent, and of a known accuracy. This will allow future researchers to better define confidence limits when applying these data. A number of parameters such as relative and absolute sea level trends will be determined from the database and made available through the ESEAS user interface.
ThE ESEAS standard is based mainly on IOC Manuals, the EOSS Position Paper, the experience gained by the WOCE Sea Level Data Assembly Centres, other international (e.g. IOC's GE-TADE and ICES WGMDM) and national expertise to derive a set of recommended standards for quality control of tide gauge data. This will result in data sets of sea level which have been acquired and processed to agreed standards and which have thereby obtained ESEAS quality endorsement.
Full document of ESEAS standard is available in (.doc) and (.pdf).
Fabio Raicich (2002) has prepared a Review of Current Quality Control Applied to Tide Gauge Data as part of ESEAS-RI Task 1.2 and Deliverable 1.2.
