Place pages display available high tides, low tides, heights and coefficients over 15 days.
Understanding forecasts
How tide times are calculated
A page to understand the calculation logic, the displayed data and the natural limits of a tide forecast.
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The tide cycle
Displayed tide times are astronomical forecasts. They are produced from the motion of the Moon and Sun, reference stations, and parameters describing the local tide response.
The method uses harmonic analysis, a scientific approach that represents sea-level variation as a combination of cycles, without constituting an official certified publication.
The calculation in 4 steps
- 1
Choose a reference station
Each place is associated with a station or reference point when one is available.
- 2
Rebuild the astronomical curve
Harmonic constituents describe the main astronomical cycles influencing that station. Combined with local parameters, they make it possible to estimate the evolution of sea level.
- 3
Detect high and low tides
The high and low points of that curve are detected to determine high tides and low tides.
- 4
Display local time and limits
Times are then displayed in the time zone associated with the station.
What are harmonic constituents used for?+
They describe how a station responds to the main astronomical cycles. They make it possible to estimate a forecast curve for sea level without representing every locally observed condition on their own.
What is displayed
The reference station or attachment point is shown to help understand where the forecast comes from.
Heights and coefficients are displayed when the available references allow a consistent estimate.
Limits to know
An astronomical forecast does not describe every local condition at sea. Atmospheric pressure, wind, swell and local configuration can affect the level actually observed.
Differences may also appear when a place is attached to a nearby station rather than an exact measurement point.
For any activity at sea, tide-time reading should be completed with local conditions, marine weather and harbor guidance.
Frequently asked questions
Useful answers before interpreting tide times.
Is the method scientific?+
Yes. It is based on harmonic tide analysis, which models the astronomical evolution of sea level from known cycles.
Why can there be a difference from the observed tide?+
Weather, pressure, wind, swell, coastline shape and attachment to a reference station can all influence the level actually observed.
How should these tide times be used?+
They provide a clear reading of the tide trend for a place. For a sea trip or sensitive decision, they should be completed with available local information.
Sources and references
| Source | Nature | Usage on the site | Coverage |
|---|---|---|---|
| Reference stations | Astronomical and local parameters | Basis for forecast calculation, time zone and place attachment | Stations used for published places |
| Reference levels for coefficients | Height and tidal-range markers | Coefficient estimation when that reference exists | Ports covered by that reference |
| Place reference set | Geographic attachment data | Place URL, place type, station or attachment point | Ports, cities and beaches published on the site |
| Forecasts calculated by the site | Results produced by the model | Tide times, heights and coefficients over 15 days | Places linked to an active station |
Each place page displays the station or attachment point used, the tide events and the applied time zone.
