Coastal Skipper and Yachtmaster Quiz · Tidal calculations
Using this table, what is the height of today's high water at the secondary port?
A tide table extract in metres. Standard port: MHWS 5.0, MHWN 3.8, MLWN 1.8, MLWS 0.6. Secondary port differences: minus 0.6 at MHWS, minus 0.2 at MHWN, minus 0.3 at MLWN, minus 0.1 at MLWS. Caption: today's high water at the standard port is 4.4 m.
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4.0 m. Secondary port differences are given for springs and neaps, and you interpolate between them. Today's 4.4 m is halfway between MHWN (3.8 m) and MHWS (5.0 m), so the difference is halfway between 0.2 m and 0.6 m: 0.4 m. It is a minus difference, so 4.4 minus 0.4 is 4.0 m.
