1. Maps & Compasses (Part 2)
Navigation Skills 1
Maps & Compasses (Part 2)

2. Summary: Maps Compasses Grid References Contour lines Types of North
Four figure grid references
Six figure grid references
The ‘National Grid’
Contour lines
Compasses
Types of North
Taking bearings

3. Grid References
If you want to give the location of an object on a map – use Grid References.
The 1km x 1km blue grids are numbered like so…

4. horizontally and vertically43 03
As you can see, grids are numbered
horizontally and vertically
To read of this grid we first take the horizontal reading, and then the vertical reading (REMEMBER AS: along the corridor, and up the stairs)

5. 6 Figure Grid References
Our reading was: 03 43
We call these 4 figure grid references.
However – this isn’t accurate enough for the sort of navigation you’ll have to do.
Instead, we use 6 figure grid references…

6. The extra 2 figures come from dividing our 1km x 1km grid into ten.03 04 41 42
Meaning that the orange cross is at…
Remembering: Along the corridor, and up the stairs…

7. The ‘National Grid’
The UK is divided into 100 kilometre grid squares, each of which is denoted by two-letter codes.
If you ever need to call Mountain Rescue (hopefully never), you’ll need to quote:
Your two-letter National Grid code (shown on the front of your map).
An estimated 6-figure grid reference.

8. Contour Lines Show the height around you.
Contour lines are added to maps.
Each line joins together points of equal altitude. (Following a contour line would keep you at the same height)
Appear at 10m intervals (or 5m intervals in flatter areas).
Contour lines which are:
Close together = Steep slope
Far apart = Gentle slope

12. CONVEX SLOPE (STEEPER AT LOWER END)

14. Compasses

15. Compasses and Types of ‘North’
There are two types of ‘North’.
Maps point to Grid North.
Compasses point to Magnetic North.
Due to changes in the Earth’s core, Magnetic North changes slowly over time, and is also dependent on where you are located on the Earth.
Currently between 2˚ to 3˚ West (2011 calculation)
Maps will also give you an estimate in degrees and ‘minutes’ (sub-division of a degree, 60 ‘minutes’ in a degree) for the year they were printed, and the estimated variation per year.

16. Converting between Grid North and Magnetic North
Provided the variations are to the West (currently the case for the UK), you can use the rhymes:
Grid to Mag > Add (the variation)
Mag to Grid > Get Rid (of the variation)

17. Setting the map in relation to the ground
Sometimes, a compass isn’t necessary!

18. Setting the map with the compass
Called ‘orientating the map’.
Place the compass on the map.
Turn the compass & map together until the red end of the needle points to north on the map.

19. Taking bearings
This allows you to find a direction (or angle) to travel from one checkpoint to another, using a compass.
Which is useful when you can’t follow anything else (e.g. paths, fences, contours, landmarks etc).
Remember there may be objects in the way of the direction you’re travelling – so you’ll have to compensate for this.

20. Taking bearings from a map1
Place the compass edge along your line of travel 2
Turn the compass housing to
match the map gridlines A B 4
To follow that bearing, hold the compass in your hand and turn until the magnetic needle is aligned with the parallel lines of the compass. Then follow the bearing arrow. 3
Read the angle from the direction of travel arrow.
(You can note this on your route cards)
Also, compensate for magnetic variation.
40˚ EAST

21. Taking bearings from a landmark
Taking a bearing from a recognisable landmark [e.g. a distinctive hill or a radio mast] enables you to find out your exact position on a path This can be done as follows:
Point the direction of travel arrow on your compass towards the landmark.
Turn the compass housing so that the top of the orienting arrow is in line with the red [north-facing] end of the needle.
Subtract the 3° difference between magnetic north and grid north [grid to map- get rid] by moving the compass housing the correct amount.
Place the base plate of the compass on the map with the straight edge touching the landmark from which the bearing was taken.
Without changing the position of the compass housing, turn the base plate on the map until the arrow on the base of the housing points to the north [top] edge of the map and is exactly parallel to the grid lines.
Where the edge of the base plate intersects the line of the footpath you are travelling on is your exact position.

22. Finding your position when lost
Examine the map carefully and note the last time that you were certain of your position, by identifying a physical feature such as a road, stream or hill. Mark this on the map.
Mark off the approximate bearing taken from that spot.
Estimate the time taken and/or distance travelled since your last known position and mark this estimated position on the map.
You should now have a fairly clear idea of where you are, but to reinforce this you can orientate the map. To do this, first set the compass to 360° and place the base plate so that the orienting lines are in line with the north-south grid lines. Next, turn the map until the north-facing part of the needle arrow points to
The map is now set exactly and it should be possible to recognise certain features such as hills [from the shape of their contours]. Take bearings from two recognisable features- your exact position is where the two lines intersect.
If you are still unsure, retrace your steps until you reach a point that you can locate on the map.

23. Backbearings
This is the most accurate way of finding your position in pathless country, however in reality the technique is rarely used as it relies upon fine weather, in which you could probably find out your position simply by looking at your surroundings anyway!
The first step in taking a backbearing is to take bearings on at least two, preferably three, known physical objects that can be identified on the map.
Convert these to the map [see compass skills 2] and draw intersecting lines.
Although you will never be accurate enough to get the three lines to intersect at one point, you will end up identifying a triangle of land in which you must be located. The most accurate fix is in the centre of this so-called ‘cocked hat’.

24. Aiming Off
In some cases, it is helpful to build in a deliberate error when navigating in pathless country. For example, if you wish to find a footbridge over a stream that is invisible, due to the lie of the land or poor visibility, until you reach it, it is best to aim to the left or right of the bridge rather than head straight for it. This is because, if you aim for the bridge but do not find it, you will not know if you have to turn left or right to reach it. If you aim to the left of it, you know that you have to turn right to get to it, and can use the stream as a ‘handrail’ to navigate by.
A similar technique that can be used in poor visibility is that of attack points. If you are aiming for a small, inconspicuous object, it is often easier to aim for a large object, e.g. a tarn, and then take a bearing to the object that you’re looking for. The attack point can be returned to if you do not find your target.