AS SEEN IN THE NOV/DEC 2007 ISSUE

Are Compasses Dispensable Now That GPS Chart-Plotters Are Dominating The Market?

A neighbor of mine – a new boater I might add – approached me a few years back and mentioned he had just purchased a pre-owned boat. “Great” I said, “So are you going to have your compass checked to make sure it’s at least in the ball park – accuracy wise?”

The somewhat surprised gentleman shrugged, “What in the world do I need a compass for? I just bought a boat with a $5,000 GPS chart-plotter – the thing does everything but make coffee.”

Similar conversations are replayed everyday by both seasoned salts and boating safety instructors, and unfortunately, I think both groups are loosing ground. Let me continue by stating the following fact in unequivocal terms; if not already part of the package, the very first piece of safety equipment that you purchase MUST be a compass - even if it is not a Federal mandate.

Just in case you’re new the boating industry, a magnetic compass is an instrument used for navigation. By reading the magnetic field of the Earth, a compass is able to tell you the direction of the magnetic field. This direction - which essentially points to the same place all over the globe, is designated “magnetic north.”

Ancient mariners realized that a compass could be used in conjunction with a marine chronometer to calculate longitude, and a sextant to calculate latitude - providing a very accurate navigation capability. This device greatly improved maritime trade by making travel safer and more efficient.

When did the needle start pointing to “North,” you ask. The origin of the compass is shrouded in mystery. Certainly the Greeks knew about the attractive properties of magnetism in ancient times. Nevertheless, the earliest compass dates back to the 11^th Century with Europeans taking credit for inventing the first maritime compass sometime in the early 1300s. The device hasn’t changed much since.

Magnetic Compass –vs- GPS/Chart-plotter

A marine compass is essentially a simple mechanical device with only one moving part. In fact, many traditional compasses have a total of only three parts, a needle that freely pivots, a pin for the needle to pivot on, and a compass rose. These three items are typically sealed in some sort of liquid filled casing which prevents the needle from fluctuating too far off course as the boat rocks back and forth, but even that’s not necessary. A compass, unless demagnetized or thrown off by a stronger local magnetic field, will always point to magnetic north. It requires no additional internal or external components and costs anywhere from $20 to $200. 

A GPS/Chart-plotter on the other hand, consists of hundreds of electrical components that must be enclosed in a weatherproof casing. A GPS/Chart-plotter requires an energy source, reception of signals from multiple satellites which can be affected by weather and electrical storms, and needs to be calibrated through the systems setup menu. A typical GPS/Chart-plotter costs $500 to over $5000.

When I kindly told my neighbor “You need a compass!” he replied, “Why? All I need to do is plug in the coordinates for my intended destination.”

In reply I stated, “Sure, the GPS will display the shortest route between here and there, which in coastal navigation is typically a straight line from Point A to Point B. But have you considered that their may be a sandbar, an island or some other sort of obstruction between Point A and Point B?” This fact alone proves why GPS/Chart-plotters are not foolproof.  

Okay, so as a novice boater you’re still not sold on the importance of a basic maritime compass. Let’s look at the skill it takes to use a compass versus a GPS/Chart-plotter.

Unequivocal factoid number two; besides “Safe Boating,” all boaters should take a basic course in simple maritime navigation. You need to be able to read a nautical chart and plot a course on such chart. With this in mind, in order to properly read a compass, you must know the direction in which you intend on traveling. That means you need to plot your course so you can ascertain the proper heading, and then point the bow of the boat in that same direction with nothing more than your compass.

Purists will tell you that you also need to apply TVMDC (True course +/- Variation = Magnetic course +/- Deviation = Compass course). TVMDC is the method of converting a true heading [that’s what you get on nautical charts] to a compass heading [that’s what your compass reads] by applying corrections for variation [the change in the magnetic field of the earth] and deviation [the local magnetic field on your boat due to radios and other electronic equipment mounted near your compass]. It sounds more difficult than it actually is, but that’s why you should further your boating education.

With a GPS/Chart-plotter, you need to plot your course, punch in each waypoint along that course, and then have your GPS/Chart-plotter tell you which way your boat should be headed. Simple, right? Not so.

First, you have to figure out how to operate your GPS/Chart-plotter. Then you have to figure out how to enter waypoints, then how to create a route. Finally, you need to know how to activate that route. Along the way, you have to know how to adjust a myriad of settings that tell the GPS/Chart-plotter how the information should be displayed to the end-user – you! By the way, most GPS/Chart-plotters provide you with a magnetic course – that’s if you’re bothering to write down the information or actually plot it on a paper chart….just in case.

Oh, I almost forgot. A GPS/Chart-plotter runs on electrical energy. Batteries die. Electrical connections deteriorate and short-out. The display can burn-out or even crack. Satellites incur problems and weather can degrade the satellite signal so you can’t acquire a strong enough signal to establish a precise fix.

A compass runs on nothing more than the magnetic field of the earth. If the magnetic field were to fail…well…you wouldn’t need to worry about the compass not working. Life as we know it would cease to exist.

Sure, there is no question that boaters of all sizes should take full advantage of modern technology and enjoy the multitude of benefits that come along with a state-of-the-art GPS/Chart-plotter, but for Heaven’s sake, if your boat is not already equipped with one, buy a compass and learn how to use it – it will be one of the smartest things you ever do!

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