Secondary Station Tide Predictions
The publication of full daily tide predictions is necessarily limited to a comparatively small number of stations. These stations are referred to as "reference stations". Tide predictions for more than 3000 other locations, referred to as "subordinate stations", can be obtained by applying specific differences to the daily tide predictions for one of the reference stations.
This section of our web site provides a listing of the more than 3000 subordinate stations for which tide predictions can be made. The stations are listed in geographical order to make it easier to find stations of interest. Once a station is selected from the list of stations available, the daily tide predictions for that station, with all adjustments applied, will be presented.
Caution: The time differences and height ratios used to calculate predictions at subordinate stations are derived from a comparison of simultaneous tide observations at the subordinate station and its reference station. Because these adjustments are constant, they may not always provide for the daily variations in the actual tides, especially if the subordinate station is some distance from the reference station. Therefore, although the application of time differences and height ratios will generally provide reasonably accurate approximations, they cannot result in predictions as accurate as those listed for the reference stations, which are based on much larger periods of analysis.
Latitude and Longitude: The geographical latitude and longitude for each station is provided in degrees and minutes. The precision to which the position is recorded is dependant on the age of the station. Advances in electronic navigation has allowed for the geographical position of tide stations to be recorded with a high degree of precision. Older stations, which were observed before electronic navigation became widely available, will have positions recorded with less precision than those more recently observed.
Mean Range: The mean difference between high and low tidal levels.
Spring Range: The mean difference between high and low tidal levels during "spring tides". Spring tides are periods of increased tidal range which occur around the dates of the full moon and the new moon.
Mean Tide Level: The arithmetic mean of high and low tides. The height of the Mean Tide Level is listed relative to the Mean Lower Low Water datum.