ABSTRACT
Secondary Port calculations build upon the process which has been started in the Standard Port examples. The Standard Ports are main ports with their own graph and calendar of predictions for the whole year. Ports are paired together by the similarity of the characteristics of their tidal curves. By interpolating for the appropriate differences in time and heights, the values for the ‘Slopy Line’ and the time of High or Low Water can be determined to use on the Standard Port curves. These tidal curves can now be assumed to apply to the Secondary Port in question, with the tidal curve now effectively referenced to the time of high water at the Secondary Port. Any height or intervals determined from the curves, will now relate directly to the Secondary Port. The process of interpolation does not come naturally to everyone but there are other times that deck officers will have to interpolate, and exactly the same method is utilised.
