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The Origin of the Compass

Dating back to the Qin dynasty of 221-206 B.C., compasses have been vital navigational aids to explorers throughout history. Without them, many pioneers would not have returned home to tell their adventures of newly discovered lands.

A navigational tool that has stood the test of time, compasses are still an important necessity to man. Although there have been many new high tech additions to compass manufacturing, basic compasses continue to be constructed and used today as they did so many years ago. From pilots and sailors to hunters and geographers, compasses are an important part of daily life.

Using a Compass

The basic use of a compass is to measure the geographic direction between two points. As easy as that sounds, it’s almost hard to believe that such a simple instrument made up of a magnet mounted on a pivot can harness the earth’s magnetic field in the palm of our hands.

And with that basic use of the compass, travelers are able to plot a map by determining the direction to a destination, stay on a straight course, and return to their starting point. Depending on the travelers likes, there are many different types of compasses available, such as baseplate, sighting, prismatic, and electronic. A baseplate compass is most commonly used by boy scouts for outdoor camping due to its affordability, the ability to navigate with ease, and because it does not require batteries.

Popular Compass Brands

While there are many manufacturers of compasses, there are a few names that stand out. Silva Compass is one of those names. The Founder of Silva Compass, or Silva of Sweden, invented the orienteering or protractor compass popularly used for outdoor navigation around the world. Silva USA was founded in 1946 and was acquired by Johnson Worldwide Associates. In the United States , you’ll find Silva products sold under the names of Brunton and Nexus, to name a few. They manufacture many general use compasses used recreationally for outdoor camping and hiking or for scientific and marine uses.

The great name of Brunton specializes in precision. Unlike other modern compasses that use fluid to dampen needle oscillation, the Brunton Pocket Transit utilizes magnetic induction damping. This revolutionary system is superior to the venerable fluid damping system found on many compasses. Because of this, the United States Army has adopted the Pocket Transit as the M2 Compass used by crew served artillery.

Another trusted name is Kasper & Richter, more commonly known as K&R Compass. Since 1920, K&R Compass has established a strong brand name among connoisseurs with their quality compasses and instruments such as altimeters and pedometers. K&R Compass works “on the basis of precision, dependability and experiences, we search for innovative solutions for better products with a high degree of curiosity and creativity.” This family owned and operated business has created a comprehensive collection of products used for counting, measuring, and providing orientation at the highest level of superiority.

Two Common Types of Compasses

Needle Compass (Pocket Compass)

A magnetized pointer, which is usually marked on the north end, is free to align itself with the earth’s magnetic field. The face is marked with the cardinal points of north, south, east, and west. Pocket compasses can use a dry magnetized needle or use a magnetized needle or dial inside a capsule completely filled with fluid such as oil, kerosene, or alcohol.

Baseplate Compass (Protractor Compass)

Built in Sweden in the early 1930’s, these compasses are made of clear plastic or Perspex. Their base is rectangular shaped with a 360 degree dial mounted upon it. This raised dial contains a magnetic needle and fluid that can be rotated in relation to the baseplate. These parts allow you to take the bearing of a landmark and measure courses on a map. Although they can seem a little tricky at first, these compasses are known for their most accurate bearings.

Tips to an Accurate Compass Reading

When traveling by ground, it is very easy to get off course by misreading a compass. A small error can become quite significant. Here are a few tips to ensure accuracy when reading a compass:

• A compass must be held level and steady. This allows for the needle to swing freely and accurately.



• Always hold a compass at waist level in front of the body, except when using a sighting type compass.



• Always use the same eye level when taking bearings. Only raise and lower eyes, never move the head.



• Directly face objects that are being measured.
  
  
• Move away from magnetic fields when reading a compass. Some magnetic fields include iron (ferrous metals), steel, rebar, clipboards, vehicles, belt buckles, glasses, and jewelry.



• Always take a bearing twice.



• Adjust for magnetic declination* as appropriate.



• Do not follow the compass needle. Follow the direction of the travel arrow when walking a bearing. Never rely on judgment for the direction, follow the line indicated by the compass.



• Use back bearings to keep on track when navigating.

*A compass needle always points toward magnetic north. On a map, north (or true north) points towards the North Pole. Magnetic declination is the difference between magnetic north and true north. Magnetic declination changes with geographic location as well as slightly changing over time. In the US , the magnetic declination usually varies between zero and twenty degrees. This adjustment must be taken when using a compass and map together for an accurate reading. Refer to the compass manual for specific instructions.

Auto / Car / Vehicle Compass

Compensation and Deviation

Automobile compasses are set to point North by the manufacturer. But a compass is a highly sensitve instrument, subject to interference common inside most vehicles, caused by metal, the engine, electricity and wiring. The auto compasses can be adjusted to compensate for interference caused by most magnetic fields.

Compensation is recommended if the deviation is more than 5 degrees, when the compass is in its normal mounting positioning. If the error is less than 5 degrees, it is sufficient to produce a deviation table.

Compensation is made with the two compensation adjuster screws "E/W" and "N/S" in order to reduce the errors caused by iron objects or other sources of magnetic disturbance. The compensation adjuster screws are situated and marked at the front "E/W" and on the right side "N/S" of the compass housing.

The slotted edge of the adjuster screws should be horizontal before starting the compensation procedure. A small non-magnetic screwdriver is provided for adjusting purposes.

When Compensating:

The vehicle should be in an area that is not affected by permanent or electromagnetic disturbances.

Have vehicle running and accessories in normal operating condition.

With adjuster screws in the neutral position and known directions available from maps/charts, landmarks or roads, adjust as follows:

1. Aim the vehicle due North and turn the "N/S" screw until the compass reading is 0 degrees.

2. Aim the vehicle due East and turn the "E/W" screw until the compass reading is 90 degrees.

3. Aim the vehicle due South. If the compass does not show 180 degrees, turn the "N/S" screw until the error is halved.

4. Aim the vehicle due West. If the compass does not show 270 degrees, turn the "E/W" screw until the error is halved.

5. Go through the procedure again and check the adjusted values.

As the magnetic conditions in a vehicle are liable to change, we recommend checking of the compass once a year and always after installation of equipment which might affect the compass.