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Setting Up A Map
The grid lines on a map are not always an indication of
north and south (unless they are actually lines of longitude and
latitude) although they are normally fairly close to it. Generally
speaking though, you can imagine that the map was made with the
direction of north going up the page. In other words, if you intend to
match up the map to your surroundings, it would be sensible to have the
map facing the correct direction. This is important if you wish to take
accurate bearings.
Note that a compass actually points to magnetic north, and not true
north and you will need to take this into account for precise bearing
and orientation work. For the time being I will ignore this magnetic
variation, and explain how to orientate the map roughly north. Even this
will help in finding surrounding features on the map.
To set up the map, that is to ensure that the map is facing north, you
will obviously need some sort of compass. I will assume we are using a
typical 'Silva' type compass.
1. Rotate the dial on the compass so that
the N marker is aligned with the direction of travel arrow at the top of
the map.
2. Place the compass on the map. Line up
the edge of the compass with a vertical (blue) grid line. (It is easier
to line up the edge of a rectangular compass rather than try to align
the direction of travel arrow with the grid line as this is partly
obscured by the dial).
3. Holding the compass and the map together
(push down on the compass gently), rotate them as a whole so that the
red arrow on the pointer (the piece that always faces north) aligns
itself with the red arrow marked on the bottom of the dial itself (there
will be some variation on this depending on what type of compass you
have).
4. As always, try to be as accurate as
possible. Look directly down upon the two arrows to line them up. When
this is done the map will now be facing north (ignoring magnetic
variation, covered elsewhere). Try to keep the map in this position
while you are using it. It is now ready for taking bearings and such
like.
The process above is not complicated. It is a simple example of using a
compass as described under bearings, except that we ensure the map also
faces this direction.
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