WHAT IS COMPASS?

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1. 1. A device used to determine geographic direction, usually consisting of a magnetic needle or needles horizontally mounted or suspended and free to pivot until aligned with the earth's magnetic field.
   2. Another device, such as a radio compass or a gyrocompass, used for determining geographic direction.
2. A V-shaped device for describing circles or circular arcs and for taking measurements, consisting of a pair of rigid, end-hinged legs, one of which is equipped with a pen, pencil, or other marker and the other with a sharp point providing a pivot about which the drawing leg is turned. Also called pair of compasses.
3. 1. An enclosing line or boundary; a circumference: outside the compass of the fence. See synonyms at circumference.
   2. A restricted space or area: four huge crates within the compass of the elevator.
   3. Range or scope, as of understanding, perception, or authority: "Lacking a coherent intellectual and moral commitment, [he] was forced to find his compass in personal experience" (Doris Kearns Goodwin). See synonyms at range.
4. Music. See range (sense ).

tr.v., -passed, -pass·ing, -pass·es.

1. To make a circuit of; circle: The sailboat compassed the island.
2. To surround; encircle. See synonyms at surround.
3. To understand; comprehend.
4. To succeed in carrying out; accomplish. See synonyms at reach.
5. To scheme; plot.

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Finding the compass that’s just right for your boat
Compasses fall mainly into two categories: fixed steering compasses and portable hand bearing compasses. There is a third type, called the telltale compass, that is built upside down and fastened to the deckhead so that a person lying in a bunk can see the ship’s course displayed overhead, but it’s now fairly rare. A small hand bearing compass on a nearby bulkhead fulfills much the same function.Steering compasses are specially made for the differing needs of powerboats and sailboats, and there is a wide choice of mounting methods. Sailboats are most often fit with binnacle-mounted compasses if they have wheel steering or bulkhead compasses if they have tillers. Powerboats often use flush-mount compasses recessed into a countertop, but small powerboats also have bracket- and surface-mounted compasses that can easily be removed.Most compasses are magnetic for the simple reason that they are reasonably priced and seldom go wrong, but there is a growing number of electronic fluxgate compasses available in all types. They work by electronically sensing the Earth’s magnetic field and displaying a digital heading; however, they are more expensive and they require DC power. Hand

Magnetic steering compasses (top to bottom): An indirect-reading compass, as seen on a sailboat’s binnacle or in a pilothouse. The course is read from the far side of the card, beneath the lubber line, and the card remains oriented to magnetic north as the boat turns. A direct-reading compass may be chosen for a bulkhead-mounted installation. It reads from the side nearest the observer, and is less intuitive to steer by than an indirect-reading compass. Acombination compass can be read either directly or indirectly. This bulkhead-mounted model includes an inclinometer for measuring angle of heel, which can affect compass readings.

A hand bearing compass.

bearing fluxgate compasses have the great advantage of being able to record and recall a number of bearings taken in succession.GPS receivers also act as compasses, of course, but only when your boat is in motion, when they provide an average of the course you have recently followed.Most magnetic compasses are internally gimballed these days, but older models with external gimbals work just as well.As a rule of thumb, the bigger the compass, the better, because it will be better damped and easier to read. The easiest compass I ever had to work with was an old-fashioned grid-steering type, which had a movable ring by which to set the course. Then all you had to do was keep the long north-south needle centered between two parallel lines. There was no parallax error, so you could sight it from almost anywhere. Sadly, grid compasses seem to have gone out of fashion in the United States, although they are still made in Europe.The worst enemies of compasses are vibration, heat, and strong sunlight. When you’re not using your steering compass, keep it shaded and cool.Some decades ago, all compasses were damped with a fluid that was primarily alcohol. The U.S. Navy’s standard type, for example, was a damping fluid that was 45 percent grain alcohol and 55 percent distilled water. When those compasses developed bubbles, you could top them off with gin. Alternatively, if you ran out of gin, you could drink the compass fluid. Don’t try that now; they’ve changed to mineral oil. Now, in a pinch, you can top off with mineral spirits or clear kerosene. And, if you run out of diesel fuel, you can make it home on the compass fluid.Compass cards for small boats don’t need gradations of less than 5 degrees. Experience has shown the human eye to be very efficient at estimating positions of single degrees on markers 5 degrees apart; anything more ambitious simply clutter

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