Secondary Ports

Most ports are listed as secondary ports, with differences applied to a standard port. The almanac provides time differences (e.g., HW is 20 minutes later) and height differences or ratios to convert standard port predictions to the secondary port.

To find tides at a secondary port: look up the standard port data, apply the time differences to get secondary port HW/LW times, and apply the height differences or ratios to get secondary port heights. Then use the tidal curve as normal.