Essential Chart Work - Tidal Stream Using a Tidal Atlas - RYA Yachtmaster Theory Training
18 February 2024 · 4 min · 1K views
What this video covers
Reading tidal stream direction and rate from a tidal stream atlas is the core skill covered, presented as part of RYA Yachtmaster theory training.0:31 The atlas is a simplified chart of a given area showing arrows indicating tidal flow direction and paired numbers indicating speed.0:46 Each page represents the tidal stream one hour before or after high water at a named reference port — in the worked example, Victoria — covering a range from six hours before to six hours after high water.1:18 Before departure, the recommended practice is to calculate the reference port's high water time and pencil the actual clock time onto each atlas page.2:18 To measure tidal direction from an arrow, a plotter is aligned across the atlas using the printed north lines, then read in the same way as on a standard chart — the example yields 271 degrees.3:15 Speed is given as two numbers separated by a decimal point: the first is the neap rate, the second the spring rate.4:01 In the example, those figures are 1.7 knots and 3.2 knots respectively.3:46 Interpolating between neap and spring rates for intermediate tidal conditions is deferred to a follow-on lesson.4:06
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