Interactive tools
Learn by doing
Some things are easier to feel than to read about. These instruments let you experiment with the core techniques of navigation right in your browser.
The plan you can read at the wheelPremium
Pilotage Plan Builder
Build the entry into Salt Sound: the leading line, the marks in the order you meet them with the side to leave each, the clearing bearing that keeps you off the sunker, and the depth sum — printed as a card.
Plan it, then sail itPremium
Passage Plan Builder
The Petrel passage as a performance rather than a reading: appraise, route on Chart SP1, time the gates, build the route card, nominate refuges — and sail the day your plan produces.
Westhaven to Salt Island
Practice Chart SP1
The course's own chart: graticule, soundings, buoyage, lights and dangers — the sheet every plotting exercise works on. Original and fictional, never for navigation.
Rule of twelfths, visualised
Tidal Height Calculator
Explore how the tide rises and falls between low and high water. Set the tide times and heights, drag the clock, and see the rule of twelfths in action — now the quick-estimate mode of the tidal curve worksheet, so you can flip straight to the port's real curve and see where the rule stops being safe.
The almanac page, workingPremium
Tidal Curve Worksheet
Work real height-of-tide problems on the Westhaven curve: height at a time, when there's enough water, spring–neap blending and secondary port corrections — graded step by step, or constructed line by line on the sheet itself.
The differences table, drilledPremium
Secondary Port Trainer
Randomised almanac-method practice: a secondary port, a day from the Westhaven table, and the corrected time and height to produce. Both interpolations graded, with the classic mistakes named rather than merely marked.
Thirteen pages of moving waterPremium
Salt Channel Stream Atlas
The tidal stream atlas for the practice chart area: hourly pages from HW−6 to HW+6, printed atlas notation, and every diamond's table — the data your course-to-steer working looks up.
The vector triangle, interactivePremium
Course to Steer Plotter
Set your desired ground track, boat speed and the tidal stream, and watch the course-to-steer triangle construct itself step by step.
Read lights like a night watchkeeperPremium
Light Characteristic Trainer
Watch animated light characteristics — flashing, occulting, isophase and more — and learn to match what you see to the chart notation.
IALA Region A at a glance
Buoyage Explorer
Browse every buoy type with its shape, colours, topmark and light rhythm, then test yourself in drill mode.
Variation and deviation without tears
True ↔ Compass Converter
Convert between true, magnetic and compass courses with a visual compass rose that shows exactly where the corrections go.