getijtafel

A getijtafel is a tide table, a tabulated prediction of sea level and the timing of high and low tides for a specific coastal location and date range. It typically lists dates, the times of high tide and low tide (in local time), and the expected tidal elevations relative to a reference datum such as NAP (Normaal Amsterdams Peil) or another chart datum.

Getijtafels are used by mariners, fishermen, harbor authorities, pilots and coastal planners to plan navigation, docking, shallow-water operations and coastal engineering. They help assess when water will be sufficient for safe passage, mooring, or dredging, and they support flood risk assessments and other shoreline management activities.

Tidal predictions are calculated from astronomical theory, taking into account the positions of the Moon and Sun and how their relative geometry interacts with local bathymetry and coastline. Because weather patterns and storm surges can modify actual water levels, observed tides may differ from the tabulated values. Historically, getijtafels appeared as printed tables in nautical almanacs; today they are published by national hydrographic offices and available in digital formats, apps and websites, often with accompanying uncertainty information.

In Dutch usage, getijtafels are common for the North Sea coast and major harbors, but similar tide tables exist worldwide. They are often complemented by getijdenkaarten or tide charts that depict water levels along a coastline rather than at a single point.