Travel by Compass

HOW A COMPASS WORKS A thousand years ago, someone noticed that a magnetized needle floating in a bowl of water would swing around to point in a northerly direction. Soon the needle became the centerpiece of the compass, and travelers had a valuable tool for helping them find their way. Today's compasses are easy to use. They work equally well in summer and winter, and are accurate at sea level, on mountaintops, and everywhere in between. Compasses available to Boy Scouts range from those for beginners to instruments for masters of navigation.
Make Your Own Ancient Compass To build a replica of the world's first compass, you'll need: 1 large sewing needle 1 bar magnet such as those found in school science classrooms 1 very small, flat chip of wood. 1 bowl of water Magnetize the needle by stroking it a few times with the magnet from the eye toward the point. Float the chip on the water. Carefully place the needle on the chip. Soon the needle will be pointing toward Magnetic North. Check the direction by looking at a compass. The needle in the compass should match the direction of the needle on the water. Using a Compass The magnetized needle of a modern compass is balanced on a pin so that it can swing freely. The needle is enclosed in a housing that rotates on the compass base plate. One end of the needle is drawn toward the Earth's Magnetic North Pole, an area about 500 miles from the true North Pole. Most compasses have an orienting arrow etched on the floor of the housing and a direction of travel arrow drawn on the base plate. Numbers on the housing indicate the 360 degrees of a circle. To find Magnetic North, adjust the compass housing until N (North) on the housing touches the direction of travel arrow, as in the photograph above. Next, hold the compass against your stomach with the direction of travel arrow pointing away from you. Turn your body until the needle is lined up inside the orienting arrow etched on the floor of the compass housing. Your direction of travel arrow is now pointing directly toward Magnetic North. Declination Compass needles point to Magnetic North. Maps are drawn with True North at the top. The difference between the direction of Magnetic North (where a compass needle points) and the direction of True North (a line between you and the North Pole) is called declination . Declination is measured in degrees -- those numbers on the compass housing. When you are in much of Wisconsin, Illinois, eastern Arkansas, or Mississippi, the directions toward Magnetic North and the North Pole are in line with one another. A compass pointing at Magnetic North seems to be pointing at the North Pole, too. Go east or west of those states and the Poles seem to move apart from one another. Declination (the difference between the direction to Magnetic North and the way to True North) increases. By the time you reach Seattle, for example, the declination is more than 20 degrees. Map margins often have two arrows, one pointing toward Magnetic North, the other toward True North. With N on the compass housing touching the direction of travel arrow, set your compass alongside the Magnetic North arrow on a map. Slowly turn the map until the compass needle rests inside the orienting arrow. The compass will be aimed at Magnetic North while the map is oriented to True North. Digital Compasses Electronic sensors inside a digital compass pick up on the Earth's magnetic fields and display accurate degree readings. Programmable adjustments automatically solve the challenge of declination. Some cellular telephones feature a compass application that acts in much the same way as the most advanced electronic route finder--the GPS receiver. GPS Receivers as Compasses Enter destination data into an automobile Global Positioning System (GPS) receiver and a map will appear on the dashboard screen showing exactly how to get to where you want to go. The GPS unit will also indicate the direction the car is moving. Handheld GPS receivers can be valuable tools for backcountry navigation, too. Type in destination coordinates and the GPS will show the way. A GPS unit can guide you even when the weather is so bad you can't see a thing. If its battery dies, a GPS unit or digital compass will be useless. That's why it is so important to learn how to use a traditional compass and to have one handy on all your backcountry adventures.