Module 10 of 17
Chartwork
Course to steer, position fixing, waypoints, dead reckoning, and estimated position.
What Is Chartwork?
Chartwork is the practical skill of plotting courses, fixing positions, and working out navigational problems on a nautical chart. It is the core of Day Skipper navigation and forms the basis of one of the two exam papers.
You need to be comfortable with plotting tools (parallel rulers, dividers, or a Breton plotter), reading chart symbols, measuring distances and bearings, and working with tidal data on the chart.
Key Points
- Chartwork = practical navigation using charts and instruments
- Forms the basis of the chartwork exam paper
- Requires parallel rulers or plotters, dividers, pencil, and rubber
Dead Reckoning (DR) and Estimated Position (EP)
Dead Reckoning (DR) is the process of estimating your position based solely on your course steered and distance run through the water — without accounting for tidal stream or leeway. It gives a basic 'where we should be' position.
An Estimated Position (EP) improves on DR by adding the effect of the tidal stream (set and drift) and an estimate of leeway (sideways drift caused by wind). The EP is more accurate than a DR position. On the chart, a DR position is marked with a cross and 'DR', an EP is marked with a triangle and the time.
Key Points
- DR = course + distance only (no tide, no leeway)
- EP = DR + tidal stream + leeway (more accurate)
- DR marked: + with 'DR' and time
- EP marked: △ with time
- Always work from a known fix when possible
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