Data logger and transmission unit

Along with tide gauges, data loggers are the other indispensable component for measuring sea level. Data loggers measure, store, process and transmit sea level measurements.


Centrale d'acquisition MORS déployé à La Pallice - La Rochelle (RONIM) entre 1997 et le début des années 2000 (Crédits Université de La Rochelle, Nicolas Pouvreau, juillet 2004). Cliquer sur l'image pour l'agrandir.


Storing sea level observations

The data logger measures water height periodically. A data item may be an average of a continuous series of measurements made during a period set by the operator, called the integration time.


Data processing

To digitally track the high-frequency signals concerning residual swell and chop, the measurements may be integrated over a time period of 2 minutes (integration time), with a measurement rate of 10 minutes (archiving period).

The average value is archived on a date corresponding to the middle of the integration period.

Principe du traitement des données (Crédits SHOM, août 2012)


Data correction

The data logger can also correct measurements based on the results of sensor calibration (water depth reduced to chart datum).


Data transmission


The data stored in the data logger can be regularly transmitted via:

  • the wired telephone network (ADSL);
  • the mobile telephone network (GPRS);
  • the radio system (VHF);
  • satellites transmitter (weather satellites).

When using satellite communications, the measurement transmission rate is set according to the conditions of the agency in charge of the satellite.

For tidal observations used in the context of a warning system (tsunamis, storm surges) two separate data transmission methods should be used to create a fail-safe system.


To find out more:



  • Simon B. (2007). La Marée - La marée océanique et côtière. Edition Institut océanographique, 434pp.



Last updated: 12/12/2012