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A HRB= 11-30 se toma Da del Faro de Punta Alcázar 136º, Ra= 086º Vhb= 6 nudos. A HRB= 12-00 se toma Da del Faro de Punta Alcázar 176º. Desvío= 3 NW dm= 3 NW. Calcular la situación a HRB= 12-00At HRB 11-30 on Ra = 086º at Vhb = 6 knots (deviation 3º NW, variation 3º NW), you take Da Punta Alcázar = 136º; at HRB 12-00 you take Da Punta Alcázar = 176º. Calculate your position at HRB 12-00:
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Correct answer: a) l = 35º-54.6' N L = 005º-34.5' W.
Why it is correct
With Ct = −3º − 3º = −6º, true course is Rv = 086º − 6º = 080º, the first true bearing to Punta Alcázar is Dv₁ = 136º − 6º = 130º and the second is Dv₂ = 176º − 6º = 170º. In 30 minutes (11:30 to 12:00) at 6 knots you run 3 miles along 080º; advancing Dv₁ by 3 miles along 080º to intersect Dv₂ gives 35º 54.6′ N, 005º 34.5′ W.
Why the others are not
- b) Does not advance the bearing Dv₁ = 130º by 3 miles along Rv = 080º to intersect Dv₂ = 170º.
- c) Does not advance the bearing Dv₁ = 130º by 3 miles along Rv = 080º to intersect Dv₂ = 170º.
- d) Does not advance the bearing Dv₁ = 130º by 3 miles along Rv = 080º to intersect Dv₂ = 170º.
How to work it out in the exam
- Compute Ct = −6º, Rv = 080º, Dv₁ = 130º, Dv₂ = 170º and distance run d = 3 miles in 30 min.
- Advance the first bearing line 3 miles along 080º to intersect the second: 35º 54.6′ N, 005º 34.5′ W.
Where this question comes from
- Junta de Andalucía · 2015 · 1ª convocatoria · PY Módulo de navegación · question 14 Official paper · Official answer key
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Pending instructor review. Machine translation, not reviewed.