14. Compass construction and siting :

Of course. This topic covers the physical makeup of a compass and the practical skill of using it to find directions to objects in the field.

Here is a detailed breakdown of compass construction and siting (often called “sighting”).

Part 1: Compass Construction

A compass is a navigational instrument that shows direction relative to the Earth’s magnetic poles. While there are many types (lensatic, thumb, digital), the most common for hiking and general use is the baseplate or orienteering compass.

Key Components of a Baseplate Compass:

1. Baseplate: The clear, flat plastic base the compass is mounted on. It has rulers (in inches, cm, and map scales) along the edges for measuring distances on a map.
2. Direction-of-Travel Arrow: A large arrow printed on the baseplate that you point at your destination. This is the most important arrow for taking and following a bearing.
3. Housing (or Bezel): The rotating circular part of the compass that is marked with 360 degrees (the cardinal points N, S, E, W are also marked). This is what you turn to set or read a bearing.
4. Magnetic Needle: The heart of the compass. It’s a lightweight, magnetized piece of metal that pivots freely. The red end always points towards the Earth’s magnetic north pole. It is often housed in a liquid-filled capsule to dampen its movement and allow it to settle quickly.
5. Orienting Arrow (The “Shed”): An arrow marked on the floor of the housing. Its job is to be aligned with the magnetic needle. A common way to remember this is the phrase “put red in the shed”—meaning, turn the housing until the red magnetic needle is inside the outline of the orienting arrow.
6. Index Line: A small line on the edge of the housing where you read the bearing in degrees. It is located at the top of the baseplate, directly in line with the Direction-of-Travel Arrow.
7. Declination Scale: A smaller scale inside the housing used to adjust for the difference between Magnetic North (where the needle points) and True North (the geographic North Pole on a map).