Leisure Fayre of Lyndhurst

Description of a map compass.

A map compass consists of two main parts, the base plate and the compass section; the compass section is designed to rotate on the base plate. On the base plate is an arrow, this will give you the direction of travel. On the face of the compass section is an arrow, and within the compass section is another arrow, which is the magnetic needle that will always point towards magnetic north.

Please learn how to use it.

1. Place the compass on the map so that the arrow on the base plate is pointing from your start point, towards your destination.

2. Swivel the compass section until the arrow on the face points to the top of the map. (The top of the map normally represents true north)

3. Remove the compass from the map, leave the settings in place, and turn the whole of the map compass until the arrow and needle in the compass section are aligned.

4. The arrow on the base plate now indicates your direction of travel.

Further Refinements

5. To correct for magnetic variation in the U.K. hold the compass firmly and move the compass section 1.5 degrees to the left.

Sighting Compass.

Description of a Sighting compass.

A sighting compass will probably have a mirror attached to the base plate, or a sight similar to a gun sight with a magnifier to read the degrees.

To find your position on a map with a sighting compass is largely a reversal of the previous instruction.

1. Identify on the map the object you wish to take a bearing from.

2. Aim the compass at the object, (a hilltop, church steeple, or lighthouse).

3. Turn the compass section until the magnetic needle and the arrow on the compass face are aligned.

4. The reading at the front of the compass is the bearing that the object is from you, therefore you are on the opposite bearing from the object. ie. If the object bears 30º from your position, you are on the opposite bearing from the object 210º

5.Without changing anything place the compass on the map so the target (a hilltop, church steeple, or lighthouse) is along the compass plate edge.

6. Turn the whole unit until the arrow on the face of the compass unit points to the top of the map and now draw a pencil line in the direction of the 'opposite bearing'

7. Repeat this process twice choosing objects that are as widely angled form each other as possible.

8. These three lines will come together as a triangle. Your position is within that triangle.

Choosing a Compass

A compass is an accurate instrument that is subject to the earth's magnetic field, this varies considerably around the world. It is important to remember that the magnetic field goes through the earth and not around it. This considerably effects the balance of the needle in the different magnetic zones.

Do not buy a compass for use in a radically different zone as the needle will be pulled either up or down, effecting the accuracy. A compass purchased in the U.K. for example will 'be pointing at the stars' in the Southern hemisphere. Silva compasses are marked for their particular magnetic zone.

Check that your intended purchase is made of anti static materials by rubbing the compass face, the needle will lock against the case if it develops a charge.

E.A.O.A. Comments and hints to add to this page are welcome

There are two forms of division on a compass, the most familiar are degrees, there is also the military 'mills' 6400 divisions to a circle. One degree equals 17.33333· mills