An updated version of the Breton Plotter or Portland Plotter, the Weems Protractor has a movable compass rose grid that can be used to lay off a course or bearing, measure distance between any two points, plot position on a chart from a given set of coordinates, or determine coordinates of position on a chart. Variation can be preset on the movable rose for ease in plotting compass bearings. The edges of the Weems Protractor are graduated in inches and centimeters. Pencil and sharpener included. Lifetime Warranty.