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This section contains a number of self-test questions on the material in Chapter 1 Navigation. For ease of use / reference, the questions are listed under the section heading where you (should have) learned to answer them! Click on the heading to go to that section.
If you click on the question itself, the answer should appear in a pop-up message, provided your browser allows such things (sometimes excluded as a security measure). Try clicking this paragraph. But if it doesn't work, have a look at the end of the page.
Some questions involve the use of a chart, so we have chosen Admiralty Leisure Folio "The Solent and Approaches" - because this Folio will be useful for a lot of people to own. The questions are set so that any equivalent charts will work, but for positions note that the Chart Datum is WGS 84.
1 True or false? "Latitude defines how far north or south you are, longitude how far east or west".
2 What is the latitude of the north pole?
3 How many degrees in a full circle?
4 A degree is divided into... how many of what sub-unit?
5 What are the lat long positions of these Isle of Wight locations:
a St Catherine's Point lighthouse;
b The Needles lighthouse;
c Yarmouth harbour entrance;
d The end of Ryde Pier;
e Saint Helen's Fort (off Bembridge).
6 True or false? "A nautical mile is defined as one minute of longitude".
7 True or False? "10 knots is faster than 10 m.p.h."
8 How many metres in a Nautical Mile?
9 What is a Cable; how many metres is a Cable?
10 What does a log measure?
1 What is South East expressed as a direction in degrees?
2 What is South West expressed as a direction in degrees?
3 True or False? "The difference in degrees between True North and Magnetic North is called Magnetic Variation"
4 True or False? "Magnetic Variation is the same everywhere in the Atlantic Ocean"
5 True or False? "Magnetic Variation at a particular location changes with time"
6 On the compass rose on a chart is printed: 5° 45' East 2006 (10' W). What is the magnetic variation in 2009?
7 You calculate that you want to steer a course of 292° True. The Magnetic Variation is 14° West. (Ignore Deviation.) What compass course do you steer?
8 You take a bearing on a landmark with the hand bearing compass: 186° Magnetic. The Magnetic Variation is 3° East. What is the True bearing to the landmark?
9 You take a bearing on a landmark with the hand bearing compass: 308° Magnetic. The Magnetic Variation is 4° West. What is the True bearing to the landmark?
10 You calculate that you want to steer a course of 055° True. Variation is 7° East. Deviation is 4° West. What compass course do you steer?
You depart the Needles Channel on a course of 148°T, headed for Ouistreham. You take a log reading by the Port-hand Lateral Buoy (50° 39.4 N 001° 37.3 W). After 1 hour you take another log reading:
1 Your boat has travelled 6.8 miles on the log. What is your DR position?
2 You are close hauled into a southerly wind. You estimate that your leeway is 4°. Which way will the leeway set you? What is your Estimated Position with leeway, ignoring tide?
3 You estimate the tidal stream for the last hour: 3.1 knots in direction 276° True. What is your EP position?
4 On that basis, what has your ground track been for the last hour?
Repeat the above questions for a passage to Alderney: you depart the same position on a course of 202° True:
5 DR after 6.8 miles?
6 EP with 4° leeway (southerly wind)?
7 EP position, with tide of 3.1 knots in direction 276° True?
8 Ground track?
9 You are a few miles from Ouistreham and the entrance to the buoyed fairway is on a bearing of 165° T. You are sailing with the wind aft of the beam, but only doing 4.5 knots through the water. The tide is setting 2.5 knots bearing 110° T. What is your course to steer? (Stick to True, don't convert to magnetic.) What will be your speed made good towards your destination?
Do this once or twice using the method illustrated, with the Breton Plotter, and see how quickly you can do it with a bit of practice. Then amaze your friends (and possibly the instructor) at the theory class. (Note: unless he has seen it before, the instructor may not believe your method works - until he works it out his way and gets the same answer.)
10 What would you do in this situation in real life - with a working GPS?
There are no concepts in this section on which to test your understanding.
Let me make a suggestion: if you haven't done so already, buy a hand-held GPS. Read the instructions and practice using it for position fixing. Be sure you know how to change the chart datum, and see how much difference using the wrong chart datum makes, when plotting your position on a chart. (It will, of course, make more difference on a small scale chart, e.g. of a harbour).
What GPS do you need?
Well you don't need any fancy maps or chart displays: any simple unit that is capable of working in nautical units and changing chart datum will do. The only functions I use on mine are: reading off latitude/longitude, waypoints (and distance and bearing to waypoint), and ground track (Course over Ground or COG).
1 You are in the West Solent and take the following bearings for a three-bearing fix: Jack in the Basket (entrance to Lymington river) 310° M; St James's Church tower Yarmouth 220° M; Hamstead Ledge buoy 076° M. The magnetic variation is 3° West. What is your position?
2 You are north of Cowes and take the following bearings for a three-bearing fix: Chimneys in East Cowes in transit on 179° M; Fawley Power Station chimney 320° M; Hill Head buoy 061° M. The magnetic variation is 3° West. What is your position?
3 In the East Solent you notice a church spire in transit with the Ferry Terminal on Ryde Pier. You see a yellow buoy less than half a mile to the south of your position, close to the transit. What is your approximate position?
4 You hurriedly take three other bearings: Fort Gilkicker 045° M; Horse Sand Fort 117° M; North Sturbridge N Cardinal buoy 104° M. The magneting variation is 3° West. Which bearing doesn't make sense? What is your position if you ignore that bearing? Assuming you read the compass correctly, can you see what would account for this gross error?
5 You pass No Man's Land Fort heading for Cowes, beating against the tide, and you want to stay as close to the Isle of Wight as possible but not go aground on Ryde Sands. Draw a suitable clearing line to No Man's Land Fort. What does the bearing to the Fort need to be, for you to be on the safe side of the line? Magnetic Variation is 3° West.
6 You use this clearing line until you are on the safe side of a second clearing line, drawn from the end of Ryde Pier. What bearing to Ryde Pier places you on the safe side of the second clearing line?
Answers
Position Speed and Distance: 1 True; 2 90° North; 3 360°; 4 60 minutes; 5 a 50° 34.52 North 001° 17.88 West; b 50° 39.73 North 001° 35.50 West; c 50° 42.42 North 001° 30.05 West; d 50° 44.38 North 001° 09.57 West; e 50° 42.30 North 001° 05.04 West; 6 False; 7 True, because 10 Nautical Miles is greater than 10 ststute miles; 8 1852 metres; 9 One tenth of a Nautical Mile, 185 metres; 10 Distance travelled through the water (in Nautical Miles); speed through the water (in knots)
Direction: 1 135°; 2 225°; 3 True; 4 False; 5 True (usually a few minutes per year); 6 5° 15' East; 7 306°; 8 189° True; 9 304° True; 10 052° Ship's compass (048° Magnetic)
How to Navigate: 1 DR: 50° 33.6 N 001° 31.7 W; 2 To the east - to port. 50° 33.8 N 001° 31.1 W; 3 EP: 50° 34.1 N 001° 35.9 W; 4 170° True; 5 DR: 50° 33.1 N 001° 41.4 W; 6 To the west - to starboard. 50° 33.3 N 001° 42.1 W; 7 EP: 50° 33.6 N 001° 46.8 W; 8 226° True; 9 192° T; approx 5.4 knots; 10 You are being set to the east, so aim off to the west (starboard) and adjust you course until course over ground (COG) is 165° T
Position Lines: 1 50 43.36 N 001 28.76 W; 2 50° 47.48 N 001° 17.45 W (you may not be afloat, but on the bright side you are unlikely to get run down by the Red Funnel ferry); 3 Approx 50° 45.5 N 001° 09.7 W; 4 The bearing to Horse Sand Fort: the other two and the transit agree with one another. 50° 45.52 N 001° 09.72 W. You incorrectly identified the sighted object: you were looking at No Man's Land Fort; 5 Greater than 104° M (101° T); 6 Less than 255° M (252° T)