Choosing a Compass for Navigation

Remember the days when you were a child and went treasure hunting with your dad’s compass, some old brass device with a card long broken? Well, these days are over and modern sailboats come with hyper-modern navigational gear. This includes compasses that don’t share more than the direction that they point at with the classic brass compasses that sailors have used for centuries.

First of all, for many boats you won’t have to choose a compass at all because it is already built in. This applies in particular for bigger yachts and serious cruisers. On the other hand, if you are more into daysailing and proud owner of a small dinghy, you won’t need to choose a compass because you simply won’t need a compass. And if you do or feel cooler with one, you will be fine with pretty many any handheld devices that you can buy from outdoor, camping or hunting stores.

On the professional side of the market, there are compasses designed and manufactured specifically for sailing vessels. One can distinguish between three types of compasses according to the kind of card they have: back-reading card, front-reading card or dome. Dome compasses are generally more common in small boats and sport vessels, because they can easily be read from different angles. The larger the card, the more accurate the course that you will be able to read – and the deeper you will have to dig in your pocket to buy the device. Card compasses should be equipped with some sort of balance aid to compensate for vibrations and heeling. There are several solutions to this problem, and once again the better ones (such as gas-cushions that make the card ‘hover’) directly correlate with the ever-growing price you’ll have to pay for them.

Only a well-calibrated compass guides you safely

In addition to the traditional card compass, some yachts come with digital devices that measure the course electronically through changes of the boat’s relation to the Earth’s electromagnetic field. For that purpose, they use a sensor generally mounted to the hull of the boat. These devices are capable of doing thousands of measurements every minute and extremely sensitive. They normally come in a package with GPS and other navigational goodies and – you guessed it – are freaking expensive.

Calibration and adjustments of compasses are another topic that the average dinghy sailor can happily ignore. However, if you just bought a yacht or a compass for one and you aim to start for a bigger tour, you should check the reliability of your compass before you set sail. The accuracy of a compass relies on its exposure to magnetic objects, which are most commonly big chunks of iron. If you place a compass on a new boat, you don’t know whether or not its environment affects it.

Follow a known route that you can precisely trace on a map and check if you compass tells you the course correctly. If not or if you are in doubt, try to find an adjustment service. Sailing accessory dealers, boat builders or sailing clubs will know local services. The same applies for people who plan to sail to the Southern Hemisphere – the compasses of the western World are generally calibrated for the Northern Hemisphere.

Further Reading

Back to "gear"

Our article on directions on a boat

DMOZ refers to other sites dealing with compasses

Wikipedia on the compass
 

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