Chart Navigation & Plotting · Plotting Tools — Parallel Rulers
Parallel rulers are used on a chart to:
- ATransfer a course or bearing line to the nearest compass rose without changing its direction✓ Correct
- BMeasure distance along the latitude scale
- CFind the depth of water
- DCalculate tide height
Explanation
Parallel rulers 'walk' a line across the chart while keeping it parallel, letting the navigator align a plotted course or bearing with a compass rose to read its direction (or vice versa). Roller and course-plotter instruments serve the same purpose.
Authority: Bowditch (Pub. No. 9), Plotting Instruments
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