Tidal Prediction Worksheet

Calculating tidal data manually using some paper form is error-prone. Wrong results are often caused by arithmetic errors creeping in whilst performing tedious calculations, by read or clerical errors and by insertion of wrong data or of correct data in the wrong field of the paper form. The Tidal Prediction Worksheet (TPW) is an EXCEL 2010 based spreadsheet to calculate tidal data for ports using the Admiralty Tide Table (ATT) method. After insertion of data from the ATT, the tides at a secondary port are computed by the TPW. For calculating the time required for meeting a given height at a port and the height at a port at a given time, the tide curves of several standard ports are included in the TPW. For standard ports not supported by the TPW, time and height are estimated by a method similar to the Rule of the Twelfths. Alternatively, a user may obtain the required data from the tide curve of the ATT to insert it into the TPW. Further manual activities, like drawing diagrams etc., are not required.

The TPW not only relieves one from tedious calculations (thus avoiding arithmetic errors) and does not confuse the inserted data, but also performs several plausibility checks for detecting absurd user inputs. For instance, the height of a LW at a secondary port exceeding the height of the HW or the user statement of non-conse­cu­tive tides for calculating the time at a port to meet a given height is recognized by the TPW. In addition, the need for user activities are minimized whenever possible, e.g. by finding the appropriate HW and LW tides when calculating the height at a port at a given time.

For working with the TPW, familiarity with the ATT method for tide calculation is assumed. Tutorials and other material about this method may be found elsewhere.

Although the Tidal Prediction Worksheet (TPW) is set up with care, it may contain errors yielding wrong results. Therefore the author does not take any responsibility at all for the correctness of the computed results. Instead it is the user’s sole re­sponsibility when relying on the outcome of the TPW for navigation or any other purposes.

Note: The TPW is only operational if these terms are accepted at the bottom of the worksheet.

© Christoph Walther                                                                                                                          Last update: 2014-02-10