In a tidal stream atlas, what do the figures 12,23 beside an arrow mean?
A page from a tidal stream atlas, headed 3 hours after HW. Arrows show the stream flowing from left to right through a channel between two coasts. Beside the heaviest arrow are the figures 12,23. A lighter arrow is marked 07,14.
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1.2 knots at neaps, 2.3 knots at springs. The figures are mean rates in tenths of a knot, neaps first and springs second. So 12,23 is 1.2 knots at neaps and 2.3 knots at springs. Between the two, work it out from the range of the tide on the day.
