The Pratt Protractor and Plotting Scale
(See page 1740 this issue)
Commander J. B. Oldendorf, U. S. Navy.—Captain Jansen's fame as a lecturer on navigation and nautical subjects is made. His subject matter could not have put all of his students to sleep as the Pratt Protractor and Plotting Scale proves. If this student has also learned one method for obtaining a line of position, then, with his protractor, he can make a plotting sheet, lay down his lines of position, and without the use of other accessories find the latitude and longitude of the fix. The device is simple and compact.
Other methods for producing a small area plotting sheet require cross-section or special paper. One method is described in Dutton's Navigation and Nautical Astronomy, p. 9, art. 12. Aviators generally use the Universal Plotting Sheet, VP-O, second edition, issued by the Hydrographic Office of the Navy Department.