A Breton plotter (French: ), also known as a Portland course plotter or Weems protractor named after later manufacturers producing similar devices, is a navigational instrument used for

nautical Seamanship is the art, competence, and knowledge of operating a ship, boat or other craft on water. The'' Oxford Dictionary'' states that seamanship is "The skill, techniques, or practice of handling a ship or boat at sea." It involves topic ...

navigation with

chart A chart (sometimes known as a graph) is a graphics, graphical representation for data visualization, in which "the data is represented by symbols, such as bars in a bar chart, lines in a line chart, or slices in a pie chart". A chart can repres ...

s. The Breton plotter contains a ruler with a rotating

protractor A goniometer is an instrument that either measures an angle or allows an object to be rotated to a precise angular position. The term goniometry derives from two Greek words, γωνία (''gōnía'') 'angle' and μέτρον (''métron'') ' me ...

that serves as a

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, allowing navigators to plot a course on charts by aligning the North of the ruler with the North of the chart.

History

The Breton plotter was invented by Captain Yvonnick Gueret, a Breton seaman who developed the plotter during his experiences teaching navigation with a () by Jean Émile Paul Cras. Gueret was a commander in merchant vessels, served on small fishing boats, delivered private yachts, and later taught navigation. While teaching, he found that students were having trouble using the more complex plotters common at the time, and decided to make his own. Gueret's device went on the market in 1979 to acclaim from publications including ''

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''. Because he did not

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the plotter, many other manufacturers released their own versions, such as the British Portland Course Plotter. Gueret later extended the use of the plotter to air navigation for small aircraft.

History

References

Further reading