For every tide station with daily tables in Ports and Passes, there are numerous secondary tide stations for which times and heights of high and low water can be found by applying a correction to a reference station. The same is true of secondary current stations.
A reference station is simply a location at which the tide or current data has been studied over a significant length of time.
Secondary tide and secondary current stations have been studied for a much shorter period of time than the reference stations. To determine the approximate values for secondary stations, it is common practice to supply a table showing the corrections which must be applied to the times and heights of high or low water or the time and speed of currents. These corrections consist of time differences, height differences, height ratios and speed ratios. If applied properly, the corrections found in the secondary tables provide reasonably accurate approximations for all navigational purposes.
These corrections are based on the average difference between the reference and secondary stations. Although the comparisons are between two stations with similar characteristics, no two stations in the world are identical. However, the tables provide reasonably accurate approximations for all navigational purposes. The differences due to meteorological conditions are probably much greater.
In previous issues of Ports and Passes, all the corrections for secondary stations were placed in the last few pages of the book. The tables were organized in a generally south to north arrangement and grouped according to the area in which they were to be found. However, there was a problem. Two secondary stations located close to each other might derive their corrections from two entirely different reference stations. The result was that a reader had to flip back and forth between two or more reference stations and the secondary correction tables.
In the 2022 and subsequent editions, we have decided to place the secondary station corrections associated with any particular reference station directly alongside the daily tables for that station. This results in much less flipping back and forth. In addition we created an entirely new method for finding the tides and currents for any location on the coast.
Refer to page v in Ports and Passes or our online guide to learn how to apply the secondary corrections. Visit our Videos page to see the video version of the guide or visit our Resources page to view and download the Quick Guide PDF version.
This new organization also allowed us to provide daily tables for five additional stations—all within the same 640 pages.
It has always been our goal to provide high-quality and easily accessible information for boaters. So, when a few boaters expressed their concern that they now found it difficult to determine the actual location of the various secondary stations, we took their concerns seriously. The result is that we have now created a Directory of Secondary Stations, listing every secondary station, the page number, the reference station to which the corrections apply and the geographic location of the station.
We hope this directory will help our readers. Safe sailing and sunny days to you all.
Visit the Directory of Secondaries Stations page to view and download the secondaries tables.
We will publish new tables each year to reflect any changes in the listings as each year, some secondary stations are no longer used, and new ones are added.