Until now, the standardised chart datum for the North Sea was uniformly referred to as LAT - Lowest Astronomical Tide. This refers to the water level that can theoretically occur - i.e. under purely astronomical conditions, without external influences such as wind or air pressure.
Important only in tidal areas
Where only very low or no measurable tides occur, for example in the Baltic Sea, such a low water level cannot be reliably determined. However, it can be determined on the North Sea coast, which is why a standardised definition is important.
Nothing changes for sailors
Apart from this new designation, nothing changes for sailors. Nevertheless, it is important to know them in order to avoid misunderstandings when navigating.
The renaming with the addition of Approximate is intended to clarify that the low water level is not an exactly calculated value, but that the reference level is approximated based on modelling and data.
Renaming only in the Netherlands
The renaming in the Netherlands has been in effect since this year, but nothing has changed in German nautical charts or documents for the time being. The Federal Maritime and Hydrographic Agency (BSH) continues to officially use the term LAT for the chart datum in the North Sea.
Lasse Johannsen
Deputy Editor in Chief YACHT
