Tidevannstabeller

Tidevannstabeller, or tide tables, are published schedules that predict the times and heights of high and low tides at specific coastal locations. They are based on astronomical calculations that take into account the gravitational forces of the Moon and the Sun, the Earth’s rotation, and the local bathymetry and shoreline configuration. The most widely used authority for these tables is the NOAA Office of Coast Survey in the United States, while other countries rely on their national hydrographic offices, such as the Swedish Hydrographic Office or the Norwegian Coastal Administration.

The tables normally include columns for date, predicted times of high and low water, the tidal range, and sometimes qualitative descriptions such as “low water” or “mid‐water.” Tide heights are expressed in reference to a standard vertical datum, typically mean sea level, and are given in meters or feet. Users must be aware of datum differences when comparing tables from different countries or regions.

Tide tables assume a stable, unmodified ocean and do not account for weather-related anomalies such as storms, wind-induced surges, or extreme waves. Consequently, marine activities often supplement the data with real‐time tide gauges or tidal models to incorporate recent measurements. For many coastal and harbor operations—fishing, shipping, offshore power generation, and recreational water sports—accurate tide predictions are essential for planning safe navigation, estimating anchorages, and coordinating tidal power generation.

The publication of tide tables dates back to the early nineteenth century, when the development of accurate chronometers and nautical charts allowed for systematic measurements. Today, most tables are derived from numerical tidal models that use a large number of harmonic constituents to achieve centimeter‑level precision at most budgets and forecast horizons up to a few days. While the basic physical principles remain unchanged, advances in satellite gravimetry and computational power continue to refine the accuracy and resolution of modern tide predictions.