Magnetic compasses range from simple and inexpensive to complex and costly.
A magnetic compass is a navigational tool used by hikers. This kind of compass works through a magnetized needle or card that orients itself with the Earth’s magnetic field. Four basic types of magnetic compasses exist: fixed dial, floating dial, orienteering and cruiser. All four types determine direction but each has special features that are specific for particular uses.
A fixed-dial compass is the least expensive compass type.
A fixed-dial compass is one of the more common of the four types of compasses. Usually, it resembles a pocket watch with a cover that protects the glass. Under the glass is a magnetized needle and a card typically showing only the four major directions. This type of compass is little better than a magnetized needle in a cork type of magnet because it does little more than point north. Problems with this type of compass include a lack of a sighting device or direction-of-travel arrow, the needle action is slow and erratic, and the compass materials are of poor quality and typically cause the needle to be inaccurate.
A lensatic compass is a mid-range magnetic compass.
A floating-dial compass has a needle and direction card attached to each other, floating freely in a liquid. This is a type you will see on the dashboard of a car. A line on the compass housing is oriented in the direction the car is going and is called the lubber line. The direction indicated on the floating needle/card with the lubber line indicates the direction your vehicle is traveling.
A second type of a floating-dial compass is a lensatic compass. It has a wire sight feature that allows the user to visually align his compass with a distant object to determine the degree reading relative to the user’s position. While this is a useful compass if you have a steady hand, other compass types are better suited for hiking.
An orienteering compass is the preferred compass used by hikers.
An orienteering compass has a needle that moves independently of the direction card and has a direction-of-travel arrow stamped in the base of the compass. The compass housing has a rotating ring that can be oriented with the direction-of-travel arrow to determine the degrees relative to magnetic north. Aside from the rotating degree ring, another feature that makes this a useful compass for hiking is that the needle is suspended in a damping liquid that keeps the needle relatively steady while walking and sighting with the compass at the same time.
To use this type of compass you point the direction-of-travel arrow at your objective, turn the degree ring until the north needle points to the 0 degree mark, and then walk in the direction indicated by the direction-of-travel arrow while maintaining the north pointing needle at the 0 degree mark.
A cruiser compass is a high-end magnetic compass.
Cruiser compasses are professional types used by surveyors and geologists. It is the most accurate and the most expensive of the four types. Because the needle is a high quality, sensitive component, this compass type has a needle lock feature when the cover is closed to prevent the needle from wearing out when the compass is not being used. The cruiser compass typically possesses several features, such as an adjustment for magnetic declinations and bubble levels and scales for determining incline, elevation, and horizontal or vertical angles. The cruiser compass is considered to be too heavy and too complex for hiking use.