Module 8 of 17
Use of parallel rulers, dividers, and proprietary plotting instruments.
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Accurate chartwork requires proper instruments. The three essentials are: parallel rulers (or a proprietary plotter like a Breton plotter or Portland plotter), dividers, and a sharp penci...
Parallel rulers are two hinged rulers that can 'walk' across the chart while maintaining a constant angle. Place the ruler along the line whose bearing you want to measure, then walk it t...
A Breton plotter (or Portland plotter) is a rotating protractor that sits directly on the chart grid. You align it with a meridian (N-S line) or parallel (E-W line) on the chart, then rea...
Dividers are used to measure distance on the chart. Open them to span the distance you want to measure, then transfer them to the latitude scale at the side of the chart (at approximately...
Keeping the chart clean is essential for safe navigation. Rub out previous workings before starting a new passage so the chart is not cluttered with old courses, bearings, and position ma...
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