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HRB= 0310, navegan con Ra= 132º y Vb= 12 nudos (corrección total= 7º W, entran en zona de niebla que solo les permite ver el faro de Trafalgar y en ese instante le toman demora de aguja a dicho faro= 037º. Continúan navegando en las mismas condiciones de rumbo, velocidad y niebla. A HRB= 0330 toman segunda Da a Trafalgar (que aún lo pueden ver)= 337º. Calculan la posición en la carta a HRB= 0330:At HRB 0310 on Ra = 132º at 12 knots (Ct = 7º W), you take a compass bearing of Trafalgar Da = 037º in fog; maintaining course and speed, at HRB 0330 you take a second bearing Da = 337º. Calculate your position at HRB 0330:
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Correct answer: a) 36º 07.1' N - 005º 59.3' W
Why it is correct
With Ct = −7º, true course is Rv = 132º − 7º = 125º, the first true bearing is Dv₁ = 037º − 7º = 030º and the second is Dv₂ = 337º − 7º = 330º. In 20 minutes (03:10 to 03:30) at 12 knots you run 4 miles along 125º; advancing Dv₁ by 4 miles along 125º to intersect Dv₂ gives 36º 07.1′ N, 005º 59.3′ W.
Why the others are not
- b) Does not advance 4 miles along Rv = 125º between true bearings 030º and 330º to Trafalgar.
- c) Does not advance 4 miles along Rv = 125º between true bearings 030º and 330º to Trafalgar.
- d) Does not advance 4 miles along Rv = 125º between true bearings 030º and 330º to Trafalgar.
How to work it out in the exam
- Compute Rv = 125º, Dv₁ = 030º, Dv₂ = 330º and distance run d = 4 miles in 20 min.
- Advance the first bearing line 4 miles along 125º to intersect the second: 36º 07.1′ N, 005º 59.3′ W.
Where this question comes from
- Región de Murcia · 2020 · 1ª convocatoria · PY Tipo 1 · question 32 Official paper · Official answer key
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Pending instructor review. Machine translation, not reviewed.