Navigation
Current triangle
Allow for a current: the course to steer to make good your track and the speed you will make, or the set and drift from what you steered and what you made good.
Fill in the fields to see the result.
How it works
The ship's motion through the water plus the current gives the motion over the ground. Set is the direction the current flows towards (tidal atlases give it that way); drift is its speed in knots.
Course to steer: the current's component across the track, c = drift · sin(set − track), is cancelled by heading into it: correction = arcsin(−c / speed). Speed made good = speed · cos(correction) + drift · cos(set − track). If the cross component is larger than the ship's speed, the track can't be held.
Example: track 000°, 10 kn, current setting 090° at 2 kn: steer 348.5°, making good 9.8 kn.
For training and cross-checking. Not a substitute for approved navigation equipment, nautical publications and the ship’s own procedures. Calculations run in your browser and nothing you type is stored; a PDF you download is made on our server and not kept.
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