QA/QC procedure

Automated procedure for telemetry data

The QA/QC procedures below are used to automatically process the environmental data from CEFAS SmartBuoys. The aim of the procedures is to produce good valid data that has passed through a series of steps that are easily understood and well documented. These steps may not remove all unwanted data but user feedback suggested that people wanted all the data with a relatively "light touch" in terms of QC. Post deployment data will undergo a fuller set of QA/QC procedures before release.

The transmission of data from SmartBuoys using the ORBCOMM telemetry system is reliable. The data rate can be set as required with a typical frequency of data every 2 to 3 hours. The ORBCOMM system uses handshaking and error checking to ensure that data corruption is extremely rare. ORBCOMM coverage is not continuous and therefore there may still be the occasional time delay for the data to reach the CEFAS server for processing.

Firstly, a comparison is made between the GPS position from the telemetry message from the buoy and the deployment location stored on the database. It these do not agree within set limits (typically 0.5 nautical mile), an "out of position" alarm email is automatically sent to the Operations Team and the data flagged appropriately.

The data are then checked against appropriate maximum and minimum values to remove the extreme values, which normally indicate the malfunction of a sensor. Data falling outside the ranges are stored to the database and flagged, but not displayed in the tables, graphs or plots.

There is an option to automatically de-spike data by checking if the absolute change from the previous data point exceeds a maximum 'rate of change' assigned to the parameter. Data falling outside the 'rate of change' criteria would be stored to the database and flagged, but not displayed in the tables or graphs.