Tide tables list times and heights for standard ports. A secondary port takes its times and heights from a standard port, with corrections. This lesson works one example end to end.
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Write the standard port data in the top row first. Every correction hangs off it.
High water at the standard port is 14:20. The secondary port lists a difference of +0:35 at 12:00 and +0:55 at 18:00. What is the corrected time?
Next: heights, and why the range matters more than the time.