Heights and streams — worked, not guessed.

20 lessons across five study days, a ten-question check closing every lesson — 200 questions over the whole of tides: why they happen and the vertical language (chart datum, height of tide, range), heights at a standard port (the tidal curve both ways and the rule of twelfths), secondary ports and clearances (under-keel and overhead), and tidal streams (the atlas, tidal diamonds and the computation of rates) — the half of tides the old track never covered. Pass a check (8 of 10) to mark a lesson complete; progress is saved on this device. The tidal-curve workbench is built into the height lessons.