Kit%20contains%20chart%20plotter%20and%20175mm%20bow%20handle%20divider.%20Provides%20a%20quick%20method%20of%20plotting%20courses%20and%20bearings%20and%20gives%20a%20direct%20reading%20of%20corrections%20for%20magnetic%20variation.%20No%20need%20to%20walk%20the%20chart%20to%20the%20compass%20rose%2C%20reducing%20error.