Tides: Overview

The ocean tide is primarily caused by the gravity of the moon and the sun. This dominant part of the tide is complex but regular and is known as the "Astronomical Tide". GeoTide predicts the Astronomical Tide using tidal harmonic analysis, meeting the SOLAS requirements. GeoTide also calculates the tidal levels; Lowest Astronomical Tide (LAT), Highest Astronomical Tide (HAT) etc. Tidal predictions and levels are important in shipping, navigation, cartography, hydrography and marine survey.

More on shipping, tidal prediction and harmonic analysis...


The remaining, unpredictable part of the tide is known as the "Residual Tide"; it is mainly caused by weather. This residual part is the difference between the observed and the predicted tide; it includes tidal surges. GeoTide uses statistical methods to analyse the residual tide and work out the likelihood of flooding. This flood probability is used in coastal planning (where it is known also as flood-return period or flood frequency) to calculate the appropriate height of sea defences, in the granting of building licenses and in the provision of insurance of coastal properties and industrial facilities.

More on flooding, return probability and sea-defences...


GeoTide handles both situations; for shipping and hydrography it produces tidal graphs, tide tables and tidal levels; for coastal flooding it produces the flood return frequency as a function of height.