Module 10 - Chartwork
Position Fixing
Active recall
Section 3 of 7
Explain the main idea from position Fixing in your own words.
A fix is a position determined from observations — it is more reliable than a DR or EP. Common methods include: visual bearings (take compass bearings of two or three charted objects and plot them on the chart — the intersection is your fix), GPS/chart plotter position, and transits.
Three bearings produce a 'cocked hat' (small triangle where the lines don't quite meet). Your position is inside the triangle. If near danger, assume you are at the corner of the cocked hat nearest the danger.
Tip: When taking visual bearings, take the bearing of the object changing most quickly first (usually the one nearest abeam), then the others. This minimises error from the boat's movement between observations.
Key points
- Fix = position from observations (more reliable than DR/EP)
- Three visual bearings give a 'cocked hat' fix
- Near danger: assume you're at the worst corner of the cocked hat
- GPS gives Lat/Long directly (plot it on the chart)
- Fix marked: ⊙ with time
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