Lecture

1. Basic Navigation Leading Cadet Training Basic Navigation Map and Compass Lecture 1

2. Basic Navigation Basic navigation is – Knowing where you are on the map. Knowing where you want to get to. Finding the best route to get there. Good navigation is a combination of: Good Map Reading Skills. Good Compass Work. Remember lines of Latitude and Longitude from your First Class Training ?

3. True or Grid North ? Lines of Latitudeget closer as they approach the North and South Poles. Grid Lines differ in that they cover a flat surface (i.e. the Map) Because of this, Grid Lines don’t actually point to the North Pole (True North) Instead they are said to point to an imaginary point called Grid North

4. Magnetic North The Earth has its own magnetic field, so a free moving needle aligns itself with this field. This needle will always point in a north/south direction. UNFORTUNATELY the magnetic north pole does not coincide with the geographical north pole (true north).

5. Magnetic North Magnetic North is in Canada. In the UK Grid North is about 5o East of True North. The other problem is, Magnetic North changes its position over time ! UK Grid North True North Magnetic North

6. Magnetic North So when navigating on a map we use Grid North

7. Magnetic Variation Magnetic Variation is different across the world. In some areas it is east of true north. So Magnetic Variation must always be allowed for when using a map and compass for navigating. To help, magnetic variation is always displayed on the bottom of an OS Map. UK Grid North True North Magnetic North Magnetic Variation

8. Magnetic Variation Because all compass references are made to either Grid North or Magnetic North, the angular difference between these 2 north's must be known. This angular difference is called the Grid Magnetic Angle (GMA) The GMA is displayed on every OS Map in the centre of the top margin. UK Grid North True North Magnetic North Magnetic Variation Grid-Magnetic Angle

9. Summary True North and south are at the geographical poles. Grid North is the direction to which all Ordnance Survey Maps are oriented. We take our map bearings using Grid North. Magnetic North is the direction a compass points to, and in the UK it is located approximately 5º West of Grid North.

10. Orientate Your Map Align your map with your surroundings, using identifiable features. Hill Woods Island Church River

11. Orientate Your Map Align your map with your surroundings, Stream junction Shoulder on a steep slope You are here Old walled enclosure Re-entrant at base of slope

12. Orientate Your Map Set the GMA against the direction of travel arrow of your Compass. Put the compass on the map and align the North-South grid lines. Turn map & compass TOGETHER until the needle falls inside the orienting arrow – red end pointing North. If you cannot set the map using observable features you can set it with your compass.

13. Finding North If you find it difficult to set your map using features on the ground, it may help to know where North is. Without a compass however, determining North is a bit tricky. You can get a rough idea of where North is by using one of the following methods…..

14. Finding North 1. The Pole Star In the northern hemisphere the North Pole is indicated by the position of the Pole Star. First find the Great Bear or Plough. Find the two ‘pointer’ stars and follow them for a distance of four times their separation. And there you find the Pole Star

15. Finding North 2. Using a Watch If you can see the Sun, hold your watch with the hour hand pointing at the sun. Half the angle between the 12 o’clock position and the hour hand points South. If you have a Digital watch, draw a diagram showing the correct time, and use that instead. Due South.

16. Finding North 3. The Shadow Method Place a stick in the ground and mark the end of its shadow. Wait for 10 to 15 minutes, and then, Mark the end of the new shadow. A line between the marks runs roughly west to east. East West

17. Check of Understanding What is navigation all about? Checking your position against GPS Knowing where you are on a map Finding your latitude and longitude Establishing your height above sea level

18. Check of Understanding The difference between true north and grid north arises because . . . Latitude and longitude lines do not match grid lines Grid lines get closer together near the Earths poles Latitude and longitude lines match grid lines exactly Lines of latitude are not parallel

19. Check of Understanding Which north changes position slightly over time? Magnetic North True North Geographic North Grid North

20. Check of Understanding Which of these symbols represents magnetic north? W X Y Z

21. Check of Understanding Which of these statements about the direction of magnetic north is true? It is the same as true north It is the same as both true north and grid north It differs from both grid north and true north It is the same as grid north

22. Check of Understanding Correctly orientating your map will help you . . . Read the contour numbers more easily Measure distances more easily Read place names more easily Find your location more easily

23. Check of Understanding Which of the following is not a method for determining north without a compass? Finding the wind direction Finding the Pole Star Using a watch and the sun Using shadows and a stick

24. Check of Understanding From the diagram, which letter indicates the correct position of the Pole Star? W X Y Z

25. Check of Understanding From the diagram, if a shadow moves from position 1 to position 2 which arrow points to the north? W X Y Z

26. Check of Understanding If you hold your watch as in the diagram, which arrow points to the north? E F G H

27. Basic Navigation Leading Cadet Training End of Presentation