Sue was sailing in the area shown on the chart on 3 March 2013. At 9:00 a.m., she sighted the antenna mast on Wellings Island on a bearing of 180°T. Sue also took a sighting to the lighthouse on Abby Island and found it was at an angle of 098°M.
(i) Sue sighted the antenna mast on a bearing of 180°T. Determine the true bearing from the antenna mast to Sue’s boat.
(ii) Steve was at the lighthouse at 9:00 a.m. on that day. What was (i) the magnetic bearing and (ii) the true bearing from Steve to Sue’s boat?
(iii) Using the information from (i), draw and label a sighting line from the antenna mast. Using the information from (ii), draw and label a sighting line from the lighthouse. Hence find Sue’s position on the chart at 9:00 a.m. Mark this position using the appropriate navigation symbol and label it with the time.
Note: Use the centre of the base of the mast symbol and the centre of the star of the lighthouse symbol as reference points.
c. At 10:50 a.m. on 10 March 2013, a vessel was at 30°30’S 150°E. From here, the vessel travelled on a course of 230ºM for 2 hours at an average speed of 10 knots. When this location was reached the vessel turned onto a heading that would enable it to reach the port at Nadia on Wellings Island.
(i) KP
Given that the variation in this area is 10°E, what was the true bearing for the first leg of this journey? How far had the vessel travelled by 12:50 p.m.? In millimetres, what length on the chart represents this distance travelled?
(ii) KP
Draw the two legs of the vessel’s journey on the chart. Label each of the lines.
(iii) KP
State the location of the vessel at its position near Sunday Island (end of the vessel’s 1st leg).
(iv) MP Level 3
If the vessel had delayed changing course until the second leg could be at 90º to the first leg, how much earlier or later would the vessel have arrived at Nadia assuming that the vessel travelled at an average speed of 10 knots through the whole trip? Give your answer to the nearest minute
To answer these questions, we will need to use some navigation concepts and techniques. Let's break down each question and explain how to get the answers step by step.
(i) Sue sighted the antenna mast on a bearing of 180°T. Determine the true bearing from the antenna mast to Sue’s boat.
To determine the true bearing, we need to consider the magnetic variation, which is the difference between true north and magnetic north at that location. The variation in this area is given as 10°E. To find the true bearing, we subtract the variation from the magnetic bearing.
True bearing = Magnetic bearing - Variance
True bearing = 180°T - 10°E
(ii) Steve was at the lighthouse at 9:00 a.m. on that day. What was (i) the magnetic bearing and (ii) the true bearing from Steve to Sue’s boat?
To find the magnetic and true bearing from Steve to Sue's boat, we need to consider the angle measurement given (098°M) and also apply the magnetic variation of 10°E.
(i) Magnetic bearing = 098°M
(ii) True bearing = Magnetic bearing + Variance
True bearing = 098°M + 10°E
(iii) Using the information from (i), draw and label a sighting line from the antenna mast. Using the information from (ii), draw and label a sighting line from the lighthouse. Hence find Sue’s position on the chart at 9:00 a.m. Mark this position using the appropriate navigation symbol and label it with the time.
To find Sue's position, we need to plot the sighting lines from the antenna mast and the lighthouse. Start by drawing a line from the antenna mast at the determined true bearing. Then, draw a line from the lighthouse at the determined true bearing. The point where these two lines intersect is Sue's position at 9:00 a.m. Mark this point on the chart with the appropriate navigation symbol and label it with the time.
(c) At 10:50 a.m. on 10 March 2013, a vessel was at 30°30’S 150°E. From here, the vessel traveled on a course of 230ºM for 2 hours at an average speed of 10 knots. When this location was reached, the vessel turned onto a heading that would enable it to reach the port at Nadia on Wellings Island.
(i) Given that the variation in this area is 10°E, what was the true bearing for the first leg of this journey? How far had the vessel traveled by 12:50 p.m.? In millimeters, what length on the chart represents this distance traveled?
To determine the true bearing for the first leg, we subtract the magnetic variation from the magnetic bearing.
True bearing = Magnetic bearing - Variance
True bearing = 230°M - 10°E
To calculate the distance traveled by the vessel, we multiply the speed (10 knots) by the time (2 hours). To find the length on the chart that represents this distance, we need to use the chart's scale. The scale will be given on the chart, and it indicates the conversion ratio between real-world distance and the chart's representation in millimeters.
(ii) Draw the two legs of the vessel’s journey on the chart. Label each of the lines.
Plot the first leg of the vessel's journey on the chart using the determined true bearing. Label this line appropriately. After that, plot the second leg of the journey, which goes from the end of the first leg to the port at Nadia on Wellings Island. Label this line as well.
(iii) State the location of the vessel at its position near Sunday Island (end of the vessel’s 1st leg).
To determine the location of the vessel near Sunday Island (end of the first leg), find the intersection point of the first leg line and the line representing Sunday Island on the chart. Mark this point on the chart.
(iv) If the vessel had delayed changing course until the second leg could be at 90º to the first leg, how much earlier or later would the vessel have arrived at Nadia, assuming that the vessel traveled at an average speed of 10 knots through the whole trip? Give your answer to the nearest minute.
To calculate the time difference if the vessel had delayed changing course until the second leg could be at 90º to the first leg, we need to determine the distance between the actual end point of the first leg and the desired end point for the second leg. Then, we calculate the time it would take to cover that distance at the vessel's average speed of 10 knots. This difference in time represents how much earlier or later the vessel would have arrived at Nadia.