Stories of explorers who never made it back from their final adventures fill history books. If you read enough of those tales, you begin to notice a common thread. They simply got lost, more often than not. A wrong turn here and a misstep there can put you and your party in harm’s way quickly. One of the best ways to prevent that possibly fatal event is to have a working knowledge of the humble compass.
The Compass through the Ages
It is widely believed that Chinese fortune-tellers of old used loadstones (a mineral composed of iron oxide that aligns itself in a North-South direction) to build the boards they used for fortune-telling. Between 221 and 206 BC, someone figured out they were better at pointing to real directions, and the compass was born.
Those early compasses were slabs marked with the cardinal points and constellations. A loadstone spoon-shaped device with a handle that always pointed south served as the needle. Several hundred years later (850 to 1050 AD), magnetized needles replaced the loadstones, and the compass forever changed navigation. Those early examples were hard to use aboard tossing and rolling ships and often only provided the most rudimentary navigational aid.
In 1269 AD, Italian inventor Petrus Peregrinus devised the first true mariner’s compass. By suspending the needle, placing it in a container to shelter it from the wind and adding a sighting device and graduated circle, navigators now had a reliable source for finding directions at sea, regardless of the weather or motion of the ship.
It was Christopher Columbus, though, who discovered magnetic north. Until he made his famous voyage to the New World, people assumed the compass indicated true north. As he traveled east to west, Columbus realized a slight deviation between what his compass indicated and what his charts told him. To this day, we still refer to the difference between magnetic north and true north as the deviation.
Using Charts with Your Compass
Years of observation also have taught us that magnetic north frequently moves. That’s why charts include the deviation in the legend. Since it changes so often, charts also indicate the amount of that change, whether it is a plus or minus (east or west of true north) and the amount of deviation at the time of the chart’s printing. With that information, you can use a 10-year-old chart and apply a mathematic equations to steer an accurate course.
Here is an example. A chart dated 1985 indicates the variation as 8 degrees westerly, with an annual increase of 5 minutes per year. That means the numerical value of variation will increase by that amount per year. So in 1990, for example, the variation would have been:
V = 8°00’W plus 5’W per year x 5 years = 8°00’W plus 25’W = 8°25’W.
If the chart’s legend indicates an annual decrease instead, then the equation uses subtraction instead of addition.
Keep in mind, those deviations are different depending on where on earth you are, which is why it is vital to have local charts.
The Humble Compass versus Modern Technology
Perhaps you are wondering at this point why anyone should care about the compass with all the electronic navigational tools at our disposal today.
The answer is simple:
Batteries die and satellites can be hard to find. You need both if you hope to survive. Do you really want to risk your life because of the failure of either one? The handheld compass is not hindered by either of those maladies.
If your travels take you far away from street signs and hamburger joints, brush up on your knowledge of this invaluable survival tool.
It may just save your life.