The Blundell Harling Portland Course Plotter is one of the most piece of equipment used in chartwork and navigation and used worldwide by practical and shore based sailors and instructors alike. The Plotter is a ruler, protractor and rotating compass dial in one.FeaturesUsed worldwide by practical and shore based instructorsBright blue directional arrow prevents accidental reciprocal bearingsEdges are graduated for tide and boat speedBase has a fixed grid so it is easy to plot latitude from your GPS systemComprehensive instructions includedDimensionsLength: 330mm / 13″Width: 130mm / 5 1/4″