Source: Dataset from Poncelet C., Billant G., Saunier A. (2021). Global estimated surfaces of Lowest Astronomical Tide (LAT) and Mean Sea Level (MSL).
Port facilities are constrained by tidal ranges and must be planned accordingly with nautical infrastructure such as breakwaters and tidal gates. A standard point of reference is the Lowest Astronomical Tide (LAT), which is the lowest sea level under average meteorological conditions. It is determined by astronomical forces, predominantly the gravitational effects of the Moon and the Sun, over a period of 18.6 years. It represents the time when the sun and the moon have an ascending and receding effect on tides due to their respective positions in the sky. LAT serves as a standard reference (chart datum) for nautical charts, meaning that all depths are measured relative to this level.
Several coastal areas have high tidal ranges due to a combination of astronomical and geographical factors. High tidal ranges occur in areas such as bays and estuaries, amplifying the tidal effect. The Bay of Fundy (Canada), Patagonia (South America), and the Gulf of Saint Malo (France) are among the areas with the highest tidal ranges. Enclosed seas and gulfs are usually subject to little or no tidal variations, such as the Mediterranean, the Baltic, the Red Sea, the Sea of Japan, and the Caribbean.
Amphidromic points, or tidal nodes, are areas where there is little difference between the high and the low tide over the astronomical period (18.6 years). There are a dozen such locations around the world, including in the North Atlantic off the coast of Newfoundland, on the northeast Pacific between Hawaii and California, and off the south-western coast of Australia.