Coastal Navigation iPad eLearning App

How to use a Breton (Portland) Plotter

Using a Breton Plotter aka Portland Plotter (aka rotating protractor) to determine a course

They say a picture is worth a thousand words – we say an animation is worth infinity! Check this out.

Here is an animation of how to use the Breton Plotter to determine a course. We use the Long Island Sound chart to determine a course from a buoy we are passing close to – to the entrance buoy to New London Harbor. We want to know the true and magnetic course. Note this is not equivalent to your heading. Heading will take into account the leeway and current. We cover how to determine your heading using the known course in our Coastal Navigation course.

Have fun with this animation and please share with your friends.

We have found that this animation is best experienced with Google Chrome.

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Coastal Navigation Course

Coastal Navigation Course


My vision for NauticEd is to provide the highest quality sailing and boating education available - and deliver competence wherever sailors live and go.
Grant Headifen
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Last updated on October 8th, 2023