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Al ser Hrb= 20:00, se toma demora de aguja al Faro de Cabo Trafalgar= 005º y en este instante la sonda marca 50 metros. La corrección total (Ct) es 5 NW. Hallar la situación observada.With the echo sounder reading 50 metres at 20:00 ship’s time, you take a compass bearing of Cape Trafalgar lighthouse = 005º (total compass error Ct = 5º NW). Find your observed position:
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Correct answer: b) l = 36º 06.8' N; L = 006º 02' W.
Why it is correct
With Da = 005º and Ct = −5º, the true bearing to Cape Trafalgar lighthouse is Dv = 005º − 5º = 000º (due south of the light, on longitude L = 006º 02.0′ W). Along that meridian, the 50-metre depth contour intersects at l = 36º 06.8′ N, L = 006º 02′ W.
Why the others are not
- a) Does not place the vessel at the intersection of the Trafalgar meridian (006º 02′ W) with the 50 m contour (36º 06.8′ N).
- c) Does not place the vessel at the intersection of the Trafalgar meridian (006º 02′ W) with the 50 m contour (36º 06.8′ N).
- d) Does not place the vessel at the intersection of the Trafalgar meridian (006º 02′ W) with the 50 m contour (36º 06.8′ N).
How to work it out in the exam
- Compute Dv = 005º − 5º = 000º: you are on the meridian of Cape Trafalgar lighthouse (006º 02′ W).
- Find the intersection south of Trafalgar with the 50 m depth contour: 36º 06.8′ N, 006º 02′ W.
Where this question comes from
- Ministerio de Transportes (Madrid) · 2025 · Convocatoria de noviembre · PER Test 1 · question 42 Official paper · Official answer key
- Ministerio de Transportes (Madrid) · 2025 · Convocatoria de noviembre · PER Test 3 · question 45 Official paper · Official answer key
Try it: Navigation calculations
Pending instructor review. Machine translation, not reviewed.