Module 8 of 17
Use of parallel rulers, dividers, and proprietary plotting instruments.
Use this module hub to choose the right lesson, then open the dedicated lesson page for the complete explanation, worked examples, FAQs, and practice questions.
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...
Unlock the complete module
Get every section, quizzes, spaced-repetition flashcards, and mock exams — one-time purchase.