A Breton plotter (French: Rapporteur Breton), also known as a Portland course plotter or Weems protractor named after later manufacturers producing similar devices, is a navigational instrument used for nautical navigation with charts. The Breton plotter contains a ruler with a rotating protractor that serves as a compass rose, allowing navigators to plot a course on charts by aligning the North of the ruler with the North of the chart.
A Breton plotter (French: Rapporteur Breton), also known as a Portland course plotter or Weems protractor named after later manufacturers producing similar devices, is a navigational instrument used for nautical navigation with charts. The Breton plotter contains a ruler with a rotating protractor that serves as a compass rose, allowing navigators to plot a course on charts by aligning the North of the ruler with the North of the chart.
Source: Wikipedia "Breton plotter" · CC BY-SA 4.0
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