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HomeworkQ & A

Junior NavigationJunior Navigation

Chapter 13Chapter 13

UnderwayUnderwayPractice Cruise – Part 2

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The homework for this Chapter consists of executing a portion of the voyage that you planned for in Chapter 11.

This Practice Cruise will provide a review of the entire course and help you prepare for the course exam.

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To complete this cruise, you will need:

• your Navigator’s notebook and the completed homework from Chapter 11;

• the pilot chart for July included with your student material;

• the Excerpts from the Nautical Almanac, contained in Appendix B of your Student Manual, for all daily data and Altitude corrections to complete the sight reductions;

• a copy of any edition of the Nautical Almanac for the “Increments & Corrections” tables;

• blank copies of the Meridian Transit Form included at the end of Chapter 9;

• blank copies of the Deck Log included at the end of this chapter;

• Universal Plotting Sheets, Sight Reduction forms and CLS plotting sheets, included with your student materials.

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Practice Offshore Cruise - Underway

The critical items in your Navigator’s notebook related to taking celestial observations are:

■ Height of eye: 10.0 ft

■ Index Error (IE): Off the Arc, 0° 01.9’ (Check before each observation)

■ Watch error (WE): f 0-13 seconds

This leg of your cruise starts on 29 June 20XX.

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1. As part of your planning, you divided this voyage into 3 segments (Chapter 11 homework, Question #2) and planned to plot each voyage segment on a separate Universal Plotting Sheet (UPS). You are near the end of the first segment of the voyage and are about to start the second voyage segment.

• Prepare UPS No. 2, using the Mid-Latitude of 37°N and Mid-Longitude of 68° W.

• From your voyage plan, you note that the variation in this area is 15° W. Plot the 15° W isogonic line using points L1 39° 00’N, Lo1 69° 20’W and L2 35° 00’N, Lo2 66° 45’W.

• You also note that this UPS includes an area where the time zone changes. Plot the appropriate time zone boundary on UPS No. 2.

• You locate two waypoints on Plotting Sheet No.2 to mark the intended course for this voyage segment. Plot and label WP1 at LWP1 38° 18.8’N, LoWP1 69° 14.3’W, and WP2 at LWP2 35° 37.5’N, LoWP2 67° 03.5’W.

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Problem 1. Continued from previous slide

a. What is the magnetic course along the rhumb line of this segment? ______

b. What should be the planned compass course along this rhumb line? ______

162°M

160°

Click to view Ships CompassDeviation Table

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2. You transfer data from your Navigator’s notebook and review the pilot chart. You note that your intended route for this segment crosses two major shipping lanes, Cape Hatteras to Virgin Rocks and Cape Hatteras to Gibraltar (Chapter 11 homework, #1h). You mark the intersection of the shipping lanes and your route with WP3 for the Virgin Rocks route and WP4 for the Gibraltar route, and check these waypoints in your GPS. You also make a note in your Navigator’s notebook to closely monitor the radar when in the region of the two waypoints, based on the captain’s standing orders regarding radar contacts.■ Plot WP3 & WP4, as well as the course these shipping

lanes cross your rhumb line course, on your Plotting Sheet #2. The data recorded in your Navigator’s notebook is:

WP3: L37° 50’N, Lo 68° 20’W. Course 058°

WP4: L36° 40’N, Lo 67° 20’W. Course 071°

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3. 0400. As you begin your watch and start the DR plot, you note the ship’s heading, psc, is 133° C and speed has been 6.8 kn. The GPS indicates a position of L 38°32.6’N, Lo 69°49.1’W. The ship’s knotmeter log reading is 0579.0. Conditions overnight have been Force 3 winds.a. What is the true DR Course? _______

b. At 0400, what is the range and bearing to waypoint WP1? ________________

• 0428. Received NOAA weather fax; logged receipt and placed copy in Navigator’s notebook.

119°

30.6 nm, 117° T

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4. 0800. The GPS indicates a position of L 38°25.0’N, Lo 69°15.8’W. The ship’s heading is 133°C and the knotmeter log reading is 0606.1. Wind is Force 3 with scattered white caps. You report the position to the captain.

• Plot the 0800 GPS Fix and DR position, and the CMG from the 0400 GPS fix on a CLS plotting sheet, using L 38°30’N and Lo 69°30’W for the mid-Lat and mid-Longitude.a. What has been the true CMG from the 0400 GPS Fix?

_____

b. What has been the speed through the water (S)? ______ (use the knotmeter log readings to determine this)

c. What are the 0800 DR coordinates? ___________________

d. What is the set and drift at 0800? ________________

106°

L38° 19.5’N, Lo 69° 18.8’W

6.8 kn

Set 023°, Dft. 1.5 kn

Click to view 0800 Set & Drift CLS Plotting Sheet Solution

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5. The current has put you off course to the northeast, so you decide to restart your DR course from the 0800 GPS fix to WP1, adjusting for current. Weather and wind conditions have remained constant so you estimate your speed (S) will continue to be 6.8 kn for this leg.

• Draw a current vector diagram to determine the true course to allow for the current determined in Question #4.

a. What is the true course from the 0800 GPS fix to

WP1, not adjusting for current? _______

b. What is the true course from the 0800 GPS fix to

WP1, adjusting for current? ________

c. What is your expected SOA? _______

d. What is the compass course to WP1, adjusting for current? ______

169° T

176° T

5.5 kn

188°

Click to view 0800 Current Vector Diagram

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6. 0910: You reach WP1 according to your GPS and change course to WP2, restarting the DR plot. You check the plotted course line between WP1 and WP2 and confirm it to be 147°T. Knotmeter log reading is 0614.0.

• You wish to check your sight-taking accuracy by getting a RFix using an LOP of the Sun now, and later in the day, a Meridian Transit of the Sun.

• At 09-15-15 you obtain a good observation on the Sun’s upper limb and record an hs of 55° 59.5’. The knotmeter reading is 0614.6.

• Reduce this sight. Use your 0915 DR position as the reference position. Plot the resultant LOP on a CLS plotting sheet, using L 38°N and Lo 69°W for the mid- Lat and mid-Longitude, and determine the 0915 EP.

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Problem 6. (continued from previous slide)

a. What is your 0915 DR position? ____________________

b. What is Ho? ________

c. What is the intercept? _____________

d. What is the azimuth? _____

e. What are the 0915 EP coordinates? ____________________

55° 41.8’

4.7 nm Toward

105°

L 38°17.1’N, Lo 69°08.1’WClick to view

CLS Plot of 0915 EP

Click to view solution onSight Reduction Form

L38°18.3’N, Lo69°13.9’W

171711/18/201211/18/2012

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7. 1000. In preparing to take a Meridian Transit sight, you want to calculate the time that transit of the sun will occur. Based on the time of yesterday’s Meridian Transit, you estimate that Meridian Transit will occur today around ZT 1140. The knotmeter log reads 0620.0. Winds have increased, waves 1-2 ft.

• Plot your expected 1140 DR position on Plotting Sheet #2, using the boat speed (S) experienced during the period 0915 - 1000.

a. What is your 1140 DR position? _____________________

b. Using your 1140 DR Lo, what is the calculated time of MT? ____________

• 1052. Received NOAA weather fax; logged receipt and placed copy in Navigator’s notebook.

L 38°03.7’N, Lo 69°01.8’W

ZT 11-39-34

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8. 1130. You prepare to take sights for the Meridian Transit and start before your calculated time of MT. You take a run of sights, selecting the observation on the sun’s lower limb at WT 11-39-48 with hs of 74° 56.1’. You note that the 1140 GPS position is L 38°03.5’N, Lo 69°02.1’W. The knotmeter log reads 0632.2, which you use to calculate your current DR position.

• Reduce the sight, using the Meridian Transit Form contained at the end of Chapter 9.

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Problem 8. (continued from previous slide)

a. What is Ho? _________

b. What is the calculated latitude from your meridian transit sight? __________

c. What is the difference between the calculated latitude from your MT sight and the latitude given by the GPS? ________

75° 10.6’

L 38°01.5’N

2.0 nm

Click to view solution onMeridian Transit Form

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9. Plot the MT observation on the CLS plotting sheet you prepared for Question #6. Advance the 0915 Sun LOP for a RFix with the 1140 MT.

a. What are the coordinates of the 1140 RFix? _______________________

b. What is the distance between the 1140 GPS fix and

the 1140 RFix? _______

• With the distance between the 1140 GPS fix and 1140 RFix small, you’re confident that the GPS is working properly. You decide to re-start your DR course line from your next GPS fix.

L 38°01.5’N, Lo 68° 56.4’W

4.9 nm

Click to view CLS Plot of 1140 RFix

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10. 1200. The GPS indicates a position of L 38°01.0’N, Lo 69° 00.0’W and the knotmeter log reading is 0634.9.Winds are Force 4 with waves 2-3 ft. After you make your entry in the ship’s Deck log and report the position to the captain, you check on the NOAA radiofax chart issued at the 1052 weather broadcast. The low pressure system that you had been following during previous forecasts, located off the Carolina coast, is developing faster than expected.

• The forecast indicates that the system is on a course of 035° at a speed of 13 mph and is predicted to cross L35° 00’N, Lo75° 00’W in 24 hours.

• After conferring with the captain, you decide to avoid the worst of the system by changing to a course of 125° T, 90 degrees to the system’s track, and increasing boat speed (S).

• Re-start your DR plot from the 1200 GPS position and locate WP5 150 miles away.

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Problem 10. (continued from previous slide)

a. What is the compass course to WP5? ________

b. What are the coordinates of WP5? ___________________________

139° C

L 36°35.0’N, Lo 66° 25.5’W

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Problem 10. (continued from previous slide)

■ Further evaluation of the weather data indicates that the system is approximately 200 miles in diameter with winds that could approach Force 5. You note that the winds will shift from the SW to S, and then to the SE as the system passes. You decide to:

• Start logging your position, either DR or GPS, every two hours until the weather system passes.

• Follow the route from the 1200 fix to WP5.

• Instruct the helmsman to follow the route as closely as possible, but to also follow the wind to minimize the strain on the boat and crew.

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11. 1400. The knotmeter log reads 0651.9. Winds are at Force 4 and increasing.

• Plot the 1400 position on Plotting Sheet #2, and make the appropriate Deck Log entry.

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12. 1600. The knotmeter log reads 0668.9 and the GPS position is L 37°54.5’N, Lo 68°17.7’W. Winds have increased to Force 5, waves to 5 ft with some spray. After plotting and logging the 1600 GPS position you compare the past two log entries with your plotting sheet. You make note that the SMG for the past 4 hours has been 8.5 kn.

You note that the 1600 GPS position is NE of the course line to WP5; this doesn’t concern you, since helmsman was instructed to follow the winds to minimize the strain on the boat and crew, and the winds from the storm have been primarily from the SW. You also note that the 1600 position is very close to the shipping lane between Cape Hatteras and Virgin Rock.

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Problem 12. (continued from previous slide)

• You immediately have the radar turned ON, and confirm it is operating and being monitored by one of the crew.

• Plot the 1600 GPS position on Plotting Sheet #2, and make the appropriate Deck Log entry.

a. What is the distance from your 1600 position to where you will cross the Cape Hatteras to Virgin Rock shipping lane? _________

4.7 nm

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13. 1614. The radar picks up a large contact at a range of 25.5 nm, on a bearing of 073°T; the GPS position at this time is L37°54.2’N, Lo68°15.4’W and the knotmeter log reads 0670.9.

Twenty minutes later, the GPS indicates your position is L37°53.6’N, Lo68°11.7’W with a knotmeter log reading of 0673.7; a second radar reading at this time indicates the contact at a range of 14.9 nm, bearing 076°T.

• Plot this situation on a CLS plotting sheet, using L 38°N and Lo 68°10’ W for the mid-Latitude and mid-Longitude.

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Problem 13. (continued from previous slide)

a. What is the ship’s course? _____________

b. What is the ship’s speed? ________________

c. What time will the ship cross your track? ________________

d. What time will your vessel cross the ship’s path?

________________________

237° (+/- 5°)

24.9 kn (+/- 1 kn)

1656 (+/- 1 min)

1719 (+/- 1 min)

Click to view Ship Crossing CLS Plotting Sheet

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• You note the ship’s closest point of approach (CPA) may be within the 4.0 nm limit of the captain’s standing orders.

e. Should circumstances require it, what true course

should you be prepared to make? _______________

f. What would be the compass course for this action? _____________

057° (+/- 5° )

Problem 13. (continued from previous slide)

(180° from the ship’s course)

073° (+/- 5°)

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• Although there appears to be no need for avoidance action, you report your position and intention to the captain. He agrees that no course change is necessary.

• 1652. Received NOAA weather fax; logged receipt and placed copy in Navigator’s notebook.

Problem 13. (continued from previous slide)

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14. 1730. The GPS indicates a position of L 37°52.1’N, Lo 68°01.8’W. The knotmeter log reads 0681.7. Winds are F5, with waves 6 ft. The ship is now well past your position.

• Checking your DR plot of the past several hours, you decide to determine the set and drift indicated by the 1600 GPS fix. You used the 1600 knotmeter log reading to calculate the speed and distance from the 1200 GPS position, and then plotted the 1600 DR and the GPS positions on a CLS plotting sheet, using L 38°N and Lo 68°30’ W for the mid-Latitude and mid-Longitude.

a. What were the 1600 DR coordinates? _________________________

b. What was the set at 1600? _____

c. What was the drift at 1600? ______

d. What was the true CMG between 1200 and 1600? _______

L 37° 41.5’N, Lo 68° 24.7’W 023°

3.5 kn

101°

Click to view1600 Set & Drift

CLS Plotting Sheet

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Problem 14. (continued from previous slide)

• You decide to change course to WP2, re-starting the DR plot from the 1730 GPS position and accounting for the newly calculated set and drift. Draw a new current diagram to determine your new course to steer and expected speed of advance to WP2.e. What will be the compass course

to steer to WP2? _________

f. What will be the speed of advance as you proceed to WP2? __________

189°

5.5 kn

Click to view 1730 Current Vector Diagram

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Problem 14. (continued from previous slide)

• You instruct the helmsman to change to this new course.

• Due to the winds and sea state, you continue the 1200 orders to the helmsman to follow the wind to minimize stress on the boat and crew. You expect the weather conditions will continue to set the boat to the NE. You decide to cover the 1600 to 1730 events by plotting only the two GPS positions for those times on the UPS sheet, and inserting a note on the UPS referencing the previous CLS plotting sheet.

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15. 1800. The knotmeter log reads 0686.0. Winds have decreased a bit but are still at Force 5 and waves are running to 4-5 ft. You review the 1642 weather fax and find that the storm is predicted to pass your present position quickly and that winds should start to moderate in the next hour.

16. 2000. You record the GPS position of L 37° 38.9’N, Lo 67° 56.0’W in the Deck Log and report this position to the captain. The knotmeter log reads 0703.0. The winds continue to moderate slightly and sea conditions improving.

• Plot your 2000 GPS position.17. 2200. The knotmeter reading is 0720.0.

Winds are at F4, with waves at 3-4 ft.

• Plot your 2200 position.

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18. 2400. You review the Deck Log, making the 2400 entry. You log the GPS position of L 37°17.7’N, Lo 67°46.8’W and the knotmeter reading of 0737.0. Winds have dropped to F3 and conditions are continuing to improve. You plot this position on Plotting Sheet #2 and label the change of date.

a. If you were to continue your watch beyond 2400, what change would need to be made in the log?

_________________________________________• Having only caught short naps throughout the storm, you turn over the watch and head to your berth for a well-earned rest.

Start a new Deck Log page, with new date.

Click to view 29 June Deck Log

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Q7Q7

End OfEnd Of Homework Homework

Q & AQ & AJunior NavigationJunior Navigation

Chapter 13Chapter 13

UnderwayUnderwayPractice Cruise – Part 2