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Course to Steer Calculator
Plot your tidal triangle in seconds. This interactive course to steer calculator lets you set the desired track, vessel speed through the water, tidal set and drift, and instantly see the heading to steer, the resulting ground track, and your projected speed over ground. Built for RYA Day Skipper and Yachtmaster students, navigation instructors, and skippers running a quick passage check.
How to use it
1. Set your desired track — the bearing you want to make good over the ground.
2. Enter your speed through the water (STW) in knots.
3. Choose how long you'll be in the tidal stream (the run time, in hours and minutes).
4. Enter the tidal set (the direction the current flows toward) and the drift (its strength in knots).
5. Read the course to steer at the bottom of the chart, along with the projected SOG and how far you'll over- or under-shoot the target.
Tip: drag to pan, use the + and − buttons or your scroll wheel to zoom, and switch between the Triangle and From start views to compare how the vectors lay out.
What the calculator shows you
Course to steer (CTS): the heading through the water that, combined with the current, makes good your desired ground track.
Crab angle: the difference between your heading and your desired track. Useful for anticipating how the bow will lie compared to where the boat is actually going.
Speed over ground (SOG): your projected speed along the desired track once the current is factored in.
Over / short vs target: when a target distance is set (manual, STW × Time, or projected SOG × Time), the read-out tells you whether the leg takes you past it or short of it.
A yellow warning appears across the chart whenever the tidal cross-current exceeds your STW — i.e. the boat cannot physically hold the desired track at that speed. Slow drift, more speed, or a different desired track is needed.
Maritime Master - CalcDeck
