Tide table is the abbreviation of tide forecast table, which predicts the daily tide situation in some coastal areas in a certain period in the future.

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Tide tables generally include daily forecast tables of main ports (usually including the time and height of high tide and low tide, and hourly tidal height in some ports), differential ratio of attached ports, tidal information and calculation of tidal height at any time.

Tidal phenomena can be regarded as the superposition of tidal components in many different periods, so the tidal height at any moment can be expressed as the height of average sea level on the tidal height datum, the circular frequency of tidal components, the intersection factor, D as the astronomical phase angle at the beginning of Greenwich, and H as the harmonic constants of tidal components-amplitude and lag angle.

In this way, the tidal harmonic constant of the port can be calculated, and the tidal time and height of the high tide and low tide and the tidal height of the hour can be calculated, and the daily forecast table can be made.

The differential number includes tidal time difference, tidal range ratio and tidal height ratio, which is obtained according to the tidal data of the main port and the auxiliary port, and can also be calculated from the tidal harmonic constants of the main port and the auxiliary port. The contrast method is a method to predict the tide in the attached port by using the tide forecast in the main port.

If you want to find the time of high tide and low tide in an attached port, you only need to add the time of high tide or low tide in the main port to the time difference of tide in this attached port. In order to obtain the high tide of high tide and low tide in the harbor, the tidal range ratio or tidal height ratio can be used to calculate.