Coastal navigation

 

The first requests for sea level information arose from the needs of inshore navigation and access to ports with substantial tidal ranges. There was a need for real-time or only slightly time-delayed measurements. 

 

Entrée de la Penfeld, Port militaire de Brest (Crédits SHOM - Nicolas Pouvreau, juillet 2012)

 

 

To meet this need, the information was obtained by direct vision:

  • Either from the tide staff available at the entrance to ports or along channels in the maritime portion of rivers;
  • Or, in the major seaports, daytime signals using cones and cylinders, and night-time signals using green, red and white lights.

 

Détail des échelles de marée positionnées à l'entrée de la Penfeld, Port militaire de Brest (Crédits SHOM - Nicolas Pouvreau, juillet 2012)

 

 

More modern systems were developed in some estuaries