Douglas Protractor, 5" Square

Called "navigational" primarily because it goes continuously from 0 to 360° as a compass rose does. Use for plotting lines of position in celestial navigation or for general plotting and vector problems on plain paper that does not have a compass rose. In England and Australia it is more commonly called a Douglas Protractor, where they are popular for general plotting. (It is said to have originated in this form in 1914 by Captain H. P. Douglas, Superintendent of Charts in the Office of the Hydrographer in the Royal Navy.)