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Douglas Navigation Protractor

 

 

 

 

 

 

An innovation by Sir Henry Percy Douglas (when he was a Captain) was the Douglas Navigation Protractor. It is a square 360 degrees protractor for plotting courses and bearings.

The Douglas protractor is designed to assist in laying of a course or bearing; reading a bearing; finding departure or latitude between two positions; finding a magnetic course; fixing graduations in 1° increments.

This protractor has proved to be an ideal navigational guide since it was invented and its use suits the present digital age. Nowadays it is made from a choice of materials and is used for example for shipping and ocean yacht racing and also air navigation.

This protractor is also ideal for making a string plotter or "Sutherland Plotter," named after Chuck Sutherland, a kayaker who invented the concept. The protractor has a small hole in the centre. Just run a light line (whipping twine or fishing line) through it, about 18 inches long, and tie a knot at both ends. Then you can use this to measure bearings and course lines from a chart. Very slick! Especially valuable for kayaks which have limited storage, but this arrangement is useful enough to be considered for all vessels



 

See also:

  • Douglas sea scale
  • Douglas-Appleyard Arcless Sextant
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    Last modified: Saturday, 18 March 2017