Note that the compass bearing to find the footpath down from
the top of Ben Nevis (the purple circle) is 280º, plus a 4º compensation for
grid north and magnetic north variation (see below). The bearing will vary
according to the exact location of your compass, either on the map, or if you
were on the actual mountain top.
The method of using a compass is very simple. The compass has a
central circular dial which rotates on a rectangular compass base. Inside the
circular dial is a magnetic needle which swivels independently, always pointing
north. So there are three items that can be rotated: the central circular dial,
the red magnetic needle, and the rectangular compass base.
Circular central compass dial with red magnetic needle
The critical Compass Reading rule: always keep the
magnetic red needle aligned with north on the dial
Only this rectangular compass base should be rotated
The arrow on this base is then used for reading and
following a bearing.
The complete compass - a very misleading, but very common
picture.
The red (magnetic) needle and north on the central circular
dial must ALWAYS be kept aligned. While keeping the red (magnetic) needle
aligned with north on the central circular dial, the rectangular base must be
rotated to read the compass bearing (in degrees) that you need to follow.
When using the compass with a map, the compass should be placed
on the exact map location you wish to take a bearing from. Align the red
(magnetic) needle with both north in the central circular compass dial and with
the grid lines running north on the map. While maintaining this alignment,
rotate the rectangular compass base until its arrow points in the direction you
wish to follow. The bearing (in degrees) should be read from the central
circular dial at the point where the rectangular compass base arrow aligns with
it. Magnetic north varies slightly both from grid north on the map and true
north (the north pole). An addition to your compass bearing of 4º will
compensate for this variation. Follow the arrow on the rectangular compass base!
Note that the direction you walk in is always the arrow on the
rectangular compass base. Remember while following a bearing to always keep the
red (magnetic) needle and north in the central circular dial aligned.
If the clouds descend while you are on the mountain, reading a
compass correctly can be a life-saving skill. In poor visibility, it is
essential to use a map and compass. Hazards can be avoided by following bearings
for distances measured from the map. Calculate the distance while you are
walking, by counting the number of paces taken and multiplying by the distance
of each pace.
Take a compass reading test with certificate
award