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A HRB = 1445 ponen rumbo verdadero 280º con la misma velocidad de máquinas de 8 nudos y en ese instante comienza a entrar niebla y ven al faro de Trafalgar por el radar en la demora verdadera = 015º; continúan navegando en las mismas condiciones de rumbo verdadero y velocidad de máquinas y a HRB 1515, toman segunda demora verdadera radar a Trafalgar = 060º. Calculan, en primer lugar, la posición sobre la carta a HRB = 1445:At HRB 1445 you steer Rv = 280º at 8 knots in fog, observing radar true bearing Dv Trafalgar = 015º; maintaining course and speed, at HRB 1515 you observe Dv Trafalgar = 060º. Calculate your position at HRB 1445:
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Correct answer: c) 36º 07.5' N – 006º 03.4' W
Why it is correct
Between 14:45 and 15:15 (30 min at 8 knots) you run 4 miles along Rv = 280º. Shifting the second bearing line Dv(Trafalgar) = 060º backwards by 4 miles along 100º true to intersect the first bearing Dv(Trafalgar) = 015º gives the 14:45 fix: 36º 07.5′ N, 006º 03.4′ W.
Why the others are not
- a) Gives the 15:15 position instead of the requested 14:45 position on the 015º bearing line to Trafalgar.
- b) Gives the 15:15 position instead of the requested 14:45 position on the 015º bearing line to Trafalgar.
- d) Gives the 15:15 position instead of the requested 14:45 position on the 015º bearing line to Trafalgar.
How to work it out in the exam
- Plot from Cape Trafalgar the two reciprocal bearings: 195º (14:45) and 240º (15:15).
- Fit a 4-mile vector on Rv = 280º between the two lines and read its start on the 14:45 line: 36º 07.5′ N, 006º 03.4′ W.
Where this question comes from
- Región de Murcia · 2019 · 2ª convocatoria · PY Tipo 1 · question 38 Official paper · Official answer key
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Pending instructor review. Machine translation, not reviewed.