Lost Art

Navigating Without Batteries —
Needle or Card? Compasses for Paddlers

By Farwell Forrest
farwell@paddling.net

June 15, 2004

Open any outfitter's catalog, and you'll probably find at least one full page of compasses. That's no surprise. Despite the microchip revolution, the magnetic compass is still an important tool for any paddling navigator. Some would say it's the most important tool. If you have a compass, you always know which way you're heading. That's pretty handy, particularly when you're trying to find your way from one place to another on the water. There aren't too many signposts on the 'Bay, after all — or on any other bay, for that matter.

OK. If you paddle, you need a compass. But which compass? And is one enough? The answer to both questions is the same: It depends. Any job is easiest when you use the right tool. You can rip lumber with a crosscut saw, but it's slow and sweaty work. It's much better to use a saw that's made for the job, and it's the same with compasses. A kayaker about to make an open-water crossing needs a different tool than a canoeist trying to find an unmarked portage trail on an island-studded lake.

So we'll answer the first question — "Which compass?" — with another: "What're you going to use it for?" Before we answer this one, though, let's step back in time for a minute and see how compasses evolved to meet the different needs of navigators at sea and ashore.

The earliest compasses were nothing more than magnetized bars or needles. One end pointed toward magnetic north. The opposite end pointed to magnetic south. Good enough for some purposes, certainly, but not exactly a precision tool. Later, when mariners began to rely on the compass to get them safely across unfamiliar seas and bring them back home again, the magnet was attached to a circular card labeled with the principal directions — not only the cardinal points of North, East, South, and West, but intercardinal (e.g., Northeast) and intermediate (e.g., North-northeast) points, and "by-points" (e.g., North by East) as well. There were thirty-two named points in all, and one of the hurdles a young officer-in-training faced was "boxing the compass," reciting all thirty-two points, first going clockwise round the compass and then in reverse order.

Paddlers may not have to box the compass, but we still make use of the cardinal and intercardinal points in naming directions, though there's not much call nowadays for "North by East," let alone the half and quarter points that further divided the intervals between the thirty-two named points. Instead, we label bearings by the number of degrees in a subtended arc, measuring clockwise from North (or 000 degrees). Since there are 360 degrees in a circle, East is 090, South is 180, West is 270, and so on. It's not very colorful, to be sure, but it has the virtue of simplicity.

In sum, early mariner's compasses had rotating cards, labeled with the points of the compass. The point falling closest to a fore-and-aft line scribed on the glass face of the compass (the "lubber line") was the ship's heading. Land navigators and surveyors — and this included the first Europeans to explore and map the waterways of North America — were more concerned with bearings than headings, however. Their compasses retained the unadorned needle of the original, supplementing it with a degree scale scribed directly on the compass housing. The north end of the needle pointed to the bearing. Whereas the mariner's compass permitted a helmsmen to hold a reasonably steady course while his ship pitched and rolled to the mid-ocean swells, the surveyor's needle made it possible to determine a bearing to a fraction of a degree. Each had the best tool for his job.

These distinctions survive to this day. Small-boat compasses have labeled cards, and headings (or bearings) are read with the assistance of a lubber line, though degrees have long since replaced points. On the other hand, compasses intended for hikers have a free-rotating needle and a fixed degree scale along the outer circumference.

Let's see how these differences work out in practice. The deck compasses used by kayakers are direct descendents of the mariner's compass. The lubber line is placed so that the boat's heading can be read from the cockpit. The graduations are relatively coarse — usually no less than five degrees — and the compass continues to point the way even when the boat is heeled to 30 degrees. Moreover, deck compasses are "liquid damped." The card (it's usually a ring or dome, in fact) is immersed in a viscous oil. This prevents the compass from spinning wildly as the boat corkscrews its way over the swells.

There are some things that the deck compass doesn't have, as well. There's no way to adjust it to eliminate variation, the difference between true and magnetic north. A deck compass gives you a magnetic heading or bearing. Period. However much this may offend fastidious navigators, who find the magnetic pole's capricious wanderings hard to bear, it doesn't matter on the water. Nautical charts usually boast one or more compass roses, and with the proper tool — a small Douglas plotter, for instance — it's easy to take a course right off your chart in degrees magnetic. It works the other way round, too. If you sight Kap Farvel over your bow on a heading of 100 degrees magnetic, you can plot the line directly on your chart, without the bother of converting. I hope you brought plenty of warm clothes.

So far so good. The coastal kayaker and her deck compass are a perfect match. The same can't be said for a canoeist trying to feel his way through a maze of islands to an inland portage, however. To begin with, chances are pretty good that his boat isn't being bounced around by three-foot swells. Nor will he often need the help of a steering compass. He can simply pick a mountain peak or a tall, lightning-scarred pine that lies in the direction he wants to go and then paddle toward it. And he won't be happy if he's forced to work solely with magnetic bearings. His topographic map doesn't have a compass rose, and the little declination diagram in the margin isn't much help if he wants to take a quick bearing. ("Declination" is the land navigator's name for "variation," the difference between true and magnetic bearings. Two names for the same thing? Yes. Confusing? You bet. But it's just an accident of history.) The canoeist would rather work exclusively with true bearings, instead. If nothing else, this will save him a lot of painstaking arithmetic.

That's why he'll choose a different compass than his sea-kayaker counterpart. Most likely it will be an "orienteering compass," one of the many collateral descendents of the familiar Silva® line. The needle rotates freely, and the navigator reads the bearing from a scale inscribed on a ring around the compass capsule. (Like mariner's compasses, most modern orienteering compasses are liquid-damped. The needle is contained in a sealed, oil-filled compartment, or "capsule." It's still livelier than a deck compass's card, however, as you'll quickly learn if you ever have to use an orienteering compass as a steering compass on a windy lake.) And unless it's a bottom-of-the-line model, the canoeist's orienteering compass will also have a declination adjustment, permitting him to dial-in the declination shown on his map. Once that's done, he can work entirely in degrees true.

Wait a minute, though. Early surveying compasses had a fixed, graduated ring. The needle pointed to the bearing. It was simple, if a little counterintuitive. The graduated scale ran counterclockwise round the compass. It still does on some contemporary compasses used by geologists and surveyors. But now take a close look at any orienteering compass. The graduated ring isn't fixed, is it? It moves if you twist it. In fact, that's how you read — or set — a bearing. You face in the direction of the object whose bearing you want, or you place the compass on your map so that one edge of the transparent base-plate connects the point where you are now with your target. Next, you twist the ring until the compass needle is enclosed in the needle-shaped outline scribed on the bottom of the capsule, or until the grid lines on the capsule lie parallel to the map grid, making sure that the north end of the compass grid points toward the top of the map. Then you read the bearing at the index mark.

It turns out that the orienteering compass is a hybrid — in some ways, it's a sort of manually-operated card compass. When you twist the ring, you're aligning the card with the needle, and the index mark serves as the lubber line. But that's where the resemblance ends. An orienteering compass permits you to determine bearings to the nearest degree, and it allows you to work directly in degrees true. No small-boat deck compass does these things.

So, which compass do you need? If you're a canoeist, and if you know you'll never attempt an open-water crossing or work with nautical charts, you'll probably be happiest with an orienteering compass. You might want to buy two, in fact. Compasses don't often fail, but when they do, it's good to have a back-up. A kayaker who plans to spend much time on tidal waters or big lakes will have different requirements. She'd better get a deck compass and a small plotter. (I'll have more to say about plotters in a later article.) When fog closes in, or when your landfall is only a dirty smudge on the horizon, it's important to be able to hold a course without depending on external reference points. That's when a deck compass earns its keep.

And while she's at it, our kayaker probably ought to pick up a sighting compass, too. It's almost impossible to take a bearing with a deck compass unless you point your bow at your target, and this isn't always a good idea. A separate hand bearing compass makes this much easier. Many of the smaller models look so much like hockey pucks that "hockey puck" is now the name that most sailors know them by. They couldn't be much simpler to use. You just aim at your target and read the bearing in degrees magnetic. Want a little more versatility? Some larger bearing compasses — Brunton's Nexus 70UNE is one — can also serve as steering compasses. It might be worth the extra weight. If a rogue wave ever washes your deck compass away, you'll be glad that your bearing compass can take its place.

Is that all there is to say about compasses? No. We're not done yet, but the rest of the story will have to wait until another time.

Deck compass or orienteering compass? Which one is best for you? It depends on what you need a compass for. And if there's any doubt in your mind, you can always get one of each. After all, the answer to the question "Needle or card?" is sometimes "Both!" That's not too hard to bear, is it? I thought not.

Copyright © 2004 by Verloren Hoop Productions. All rights reserved.