Parallel rules transfer a bearing from the compass rose to the chart without calculation, by walking the rule across the chart. Course plotters combine bearing measurement and distance in one instrument and work independently of a compass rose, which makes them better suited to smaller charts and tighter chart tables. Both have their place.
We stock parallel rules from Weems & Plath in 12 to 24-inch lengths and a range of course plotters including the Blundell Harling Portland Course Plotter, the Weems & Plath GPS Plotter and the ParaLock. The Portland is widely used on RYA Day Skipper and Coastal Skipper courses. The 15-inch parallel rule is the most versatile starting point for a standard chart table.
