Compass Basics

Compass Basics

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What's What

  • 1. The base plate mounting of the compass, with a ruler for measuring scale.
  • 2. The compass housing contains the magnetic needle and has the points of the compass printed on a circular, rotating bezel.
  • 3. The compass needle floats on liquid so it can rotate freely, the red end should always point to magnetic north.
  • 4. Orienting lines fixed within the compass housing and designed to be aligned with the vertical grid lines on a map. Half the lines are coloured red to indicate north.
  • 5. Orienting arrow fixed within the compass housing, aligned to north on the housing.
  • 6. The index line fixed within the outer edge of the compass housing as an extension of the direction of travel arrow. It marks the bearing you set by rotating the compass housing.
  • 7. Magnifier for detailed map reading.
  • 8. The direction of travel arrow shows the direction that you want to travel along or the bearing you are taking. It is fixed parallel to the sides of the base plate and aligned with the fixed index line on the edge of the compass housing (number 6).
  • 9. Compass scale displayed along the edge of the base plate so you can measure distances on maps.
  • 10. Luminous strip to assist navigation at night.

Compasses come in all shapes and sizes and they all basically do the same thing … they have a needle on them that points North, so any old Compass will do right? … well Yes, ‘Any old Compass’ is better than ‘No Compass’ … just like using a Sundial to tell the time is better than not having a Sundial.

Cardinals and Ordinals

We all know the Cardinal points of a compass, we may not know them as “Cardinal” points but that is the actual name given to North, South, East and West.

In a navigation situation, you would be extremely lucky if your route was simply made up of Cardinal points … but that’s fine, that’s why we have Ordinal points (sometimes referred to as ‘Intercardinal points’), not quite as memorable as Cardinal points but most people are quite familiar with “North East”, “South East”, “South West” and “North West” … those diagonal directions in between North, East, South and West.

Sometimes, the four Cardinal points and four Ordinal points are simply not precise enough, in such times we may choose to extend into Secondary Intercardinal’s … the directions that sit between each Cardinal Point and an Ordinal point, as such, we would always refer to the Cardinal point first and the Ordinal point second … resulting in our eight Secondary Intercardinal points being:

  • North – North East
  • East – North East
  • East – South East
  • South – South East
  • South – South West
  • West – South West
  • West – North West
  • North North West

When all Sixteen points are not precise enough … that is when we may be tempted to use Bearings.

NB: We have an entire learning module dedicated to Bearings.


Red in the Shed

Putting the Red in the Shed is a colloquial term which describe the basic method of using a compass.

Take a look at the image on the right, note the two numbered components of the compass.

  1. Red. The red end of the compass needle is the business end, usually coloured Red and always pointing North when the compass is laid on a flat surface.
  2. The Shed, it looks a little bit like the pointed roof of a shed but is actually known as the Orienteering Arrow. Note that it always points at the N on the Compass Housing (or rotating bezel).

How to put the Red in the Shed

There are two ways in which we can put the Red in the Shed …

  1. we can spin the Compass housing or Bezel until the shed surrounds the Red.
  2. We can spin the entire base plate of the compass until the Red is in the Shed.

Why is it so important to get the Red in the Shed?

Once the Red is securely in the Shed, our Compass is aligned, prior to that, the only thing that we could rely upon was the fact that the Red end of the Needle was pointing North.

Now, with the Compass aligned, we can focus our intention on the Index Line … this little line is crucial, it is always aligned to the Direction of Travel Indicator (The big arrow in the top, centre of the image on the left).

On the example image, it shows that the Direction of Travel indicator is nearly pointing in a South West Direction (SW)… or to be more precise, it is pointing along a bearing of 215 degrees.

We can rotate the baseplate wherever we want but as long as the Red is in the Shed then the Index Arrow will tell us the direction or bearing that we are looking in or intending to travel in.

Bearings will be discussed in greater detail in another Learning module.

PS. The Black ring on the image is meaningless for this exercise, Compass manufacturers often confuse people by trying to put unnecessary features on their compasses.

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