Kayak Navigation Part 2 – Compass Use and Dead Reckoning

by Nancy Soares on August 20, 2012

by Tsunami Ranger John Lull

Kayak outfitted with marine compass and chart.

Kayak outfitted with marine compass and chart.

In Part 1, I covered navigation by line-of-sight, using visual references, ranges, and no tools beyond a chart.  This works fine until visibility is reduced by thick fog or when paddling in open water well offshore or on a long crossing.  In those situations, you’ll need some other technique to navigate.  I’ll cover the basic method using a compass and chart in this article.

Using a Compass

Compass reads 140 (SE).

Compass reads 140 (SE).

Reading a compass is very simple.  Point it in a specific direction and read the dial.  For kayaking, the best choice is a deck-mounted marine compass.  A marine compass will have a large easy-to-read dial (compass card) and reading it is a hands-free operation, so you can do so while paddling.  Mount the compass with the ‘lubber line’ parallel to the keel of the kayak so wherever you point your bow will correspond with what the compass reads.  This is your heading.

Keep in mind the compass reads magnetic north (not true north).  If you use a nautical chart it will have a compass rose printed on it, with an outer circle reading true north and an inner circle reading magnetic north.  Simply use the inner rose when plotting course lines and those course lines will match what your compass is reading (both will be magnetic north).

There are two basic ways to use a compass on the water.  One way is to point your kayak at your destination if you can see it, or if not, a landmark on the way to your destination, and note the heading.  Let’s say the heading is 140 (SE).  Now if the fog rolls in, obscuring everything, you continue paddling with a heading of 140 to maintain your course.  The other way is to plot a course on your chart ahead of time, then follow that course on the water using your compass.

In both cases you’ll need to maintain the compass reading while paddling.  This is easy enough in flat water and calm conditions.  In rougher conditions the compass card will tend to sway a bit back and forth.  In that case, allow the reading to sway back and forth 5 or 10 degrees, keeping your heading in the middle.  So if the heading you want is 140, and you allow the compass to sway back and forth between 135 and 145, you will maintain a heading of 140 (it averages out).  This is much easier than trying to force the compass to stay right on 140 and it is still very accurate.  You’ll find you don’t need to constantly stare at the compass, just keeping checking it as you go.

Compass rose on chart, used for plotting course lines. Use the inner rose for magnetic north (what the compass will read).

Compass rose on chart, used for plotting course lines. Use the inner rose for magnetic north (what the compass will read).

Plotting a Course

Plot your course lines on the chart during the trip planning stage, so all you have to do on the water is glance at the chart for your heading.  Using a straight edge, draw a line from your starting point, or several lines if course changes are necessary, then use a parallel ruler to step over to the compass rose and read the course direction off the inner rose (mag north).  Label the course line and you’re all set.  You can also tick off nautical miles along the course line, using a pair of dividers, so you know the distance.  One nautical mile = one minute of latitude (NOT longitude).  It also is equal to 1.15 statute miles.

Course line plotted from Pt Sur to Hurricane Pt. Course is 340 (NNW). Nautical miles are ticked off; total distance 3 miles.

Course line plotted from Pt Sur to Hurricane Pt. Course is 340 (NNW). Nautical miles are ticked off; total distance 3 miles.

With the course line(s) plotted, your chart has the information you’ll need to navigate using a compass.

Course line was plotted using a parallel rule to determine the direction from the compass rose. Distance can be ticked off with a pair of dividers.

Course line was plotted using a parallel rule to determine the direction from the compass rose. Distance can be ticked off with a pair of dividers.

Paddling Speed

You’ll need to know your paddling speed to help keep track of how much distance you’ve covered and to estimate how long it will take you to get to where you’re going.  You can easily figure out your paddling speed by timing yourself over a known distance.   Here’s the formula:

Speed In Knots = Distance (nautical miles) X 60 (min/hr) / Time (minutes)

If you paddle 1 nautical mile in 20 minutes, your speed is 1 X 60/20 = 3 knots.  If you do it in 15 minutes, your speed is 1 X 60/15 = 4 knots.

When determining your paddling speed, I suggest paddling at a comfortable rate that you know you can maintain over a considerable distance.  That will be your ‘cruising speed.’  Most relatively experienced sea kayakers (in a typical sea kayak) have a cruising speed of about 3 knots.  Strong paddlers can maintain a speed of 4 knots or slightly more, at least for an hour or two.

Dead Reckoning

“Reckon wrong and you’re dead” – Navy Seal Richard Marcinko’s definition.

Dead Reckoning is a method of deducing your position, based on speed, time underway, and course.  We actually do a form of dead reckoning all the time when driving a car.  If someone asks me how to get to Santa Cruz from Half Moon Bay, I’ll tell them to drive south on Hwy 1 for an hour.  Their speed is 50 mph, their course is south on Hwy 1, and in one hour they will cover the 50 mile distance to Santa Cruz.

When navigating on the water, you know your paddling speed, can keep time with a waterproof wristwatch, and can follow a specific course using your compass.  I’ve already covered how to use a compass, plot a course, and determine your paddling speed.  I assume you can read a watch, so now you have all the tools you need for dead reckoning.  So, for example, say you want to paddle to an island that lies 3 nautical miles offshore and you plot a course that reads 270 (W) from your launch site to the island.  Now you have the information you need, even if the island is obscured by fog.  Simply follow a compass course of 270, maintaining a steady speed of 3 knots, and in one hour you should arrive at the island.  This is more accurate than you might think, but with increased distance and time, the margin of error increases, so it’s always a good idea to shoot for the largest target possible.  Instead of setting a course for one end of the island, set your course closer to the middle.

Cross wind or current will complicate the situation because it will set you off course.  If crossing with a strong side wind, alter your heading by 10 or 15 degrees (depending on wind strength) into the wind to compensate.  When crossing a current (usually only an issue in inland waterways subject to tidal currents), there is an easy way to calculate your ferry angle into the current, but that is beyond the scope of this article.  You can refer to chapter 11, page 155 in my book, Sea Kayaking Safety and Rescue for the method.  If you can find a range (see Part 1), even for part of the crossing, you can immediately determine the ferry angle and what the heading should be when crossing wind or current.

GPS

GPS devices are very accurate and can provide an excellent navigation tool for kayaking.  Since they are electronic devices and subject to failure in the marine environment, you will definitely want to back them up with a compass and the techniques I have discussed above.

The advantage of a GPS unit is it can give you all the info you need to navigate, including speed, distance paddled, course, location, etc.  But they do have some disadvantages and limitations.  In flat, calm conditions they are fairly easy to use, but in rough conditions, where you want to keep both hands on the paddle, punching tiny buttons and reading a small digital display can be difficult at best.  If you lose the signal for any reason, you’re out of luck.  So be sure to learn the traditional, time-tested navigation methods first; then if you get a GPS, you’ll still have some backup.

On a final note, like everything in kayaking, you have to learn by doing, so get out on the water and practice using a compass, ranges, paddling a course, and other methods I’ve covered.  You’ll also find that you can mix some of the techniques, depending on the situation.  You might use the compass for one stretch, and pick up a range for another.  Knowing how to read a chart, plan a trip, and navigate accurately will give you the ultimate freedom on the water.  You won’t have to rely on someone else to guide you!

Please feel free to comment and ask questions.

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{ 18 comments… read them below or add one }

Nancy Soares August 20, 2012 at 7:05 am

Once again, great post, John. Thanks for a clear, well-written description of some very pertinent information. Great pics, too!

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PeterD August 20, 2012 at 10:04 am

Thanks for the post. Very useful.

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Tony Moore August 21, 2012 at 7:11 am

Good point about not relying on a GPS and being familiar with the more “traditional” means of navigation. I expect there have been many GPS-only navigators perplexed that the GPS was telling them to point their bow at some angle to their visual destination. If they were familiar with traditional navigation, they’d know that a cross-current or wind was at play, and the GPS was setting the proper ferry angle.
Tony

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Nancy Soares August 21, 2012 at 8:10 am

That’s right, Tony. In fact, John and I talked about a post addressing how to calculate ferry angle when crossing current. Eventually we’ll get that info out as well.

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John Lull August 23, 2012 at 8:41 am

Tony, yes, thanks for pointing that out. It’s very true, and that brings up another point about using GPS. When used properly, it will take care of things to the extent you don’t need to understand what’s going on (until the GPS fails for any reason!). Course (the actual direction you are going) vs heading (where the boat is pointing) is a good example. Course and heading coincide when wind or current is not pushing you off course, but with a side wind or current, they will differ. I think it’s a good idea to understand this is happening, though.

Also, as I mentioned in Part 1, if you are paddling into a strong current or headwind and not getting anywhere, a range will tell you this immediately. So will GPS, but it won’t tell you why. It’s pretty obvious with a headwind, but not so clear with current when you don’t realize what direction the current is going.

Please, everybody who reads these navigation posts, if you have any questions or observations, ask or share them with us. By necessity the articles are short and a lot of crucial info could be added or clarified.

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Kayaker August 25, 2012 at 11:06 pm

I never really learned how to use a compass. What is the difference in magnetic north to true north? And what should we follow if ever we lost our way.

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Tony Moore August 26, 2012 at 7:21 am

True north is related to the spin axis of the earth. For any location on earth, true north is the direction where this axis emerges at the north pole. Magnetic north is a bit more tricky, as it depends where on the earth you are located. If you have a nautical chart, it should have a compass rose that plots out in two circles true north and magnetic north. For most locations, there is some deviation in these two “norths”, (for example 10 degrees). Other nautical charts for other locations on earth may have different deviations, (for example maybe 15 degrees). And there are some places on earth where true north and magnetic north coincide (no deviation). The point is this: when you are navigating using a compass, you should have a nautical chart for that area, and since you are using a magnetic device (the compass), use the inner circle (magnetic north circle) of the compass rose to plot any courses. John is the real pro here, he probably has some further observations on this subject.
Tony

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John Lull August 26, 2012 at 9:36 am

Good question Kayaker, and Tony gave you the answer. I’d just add that the reason there is a difference is the earth’s magnetic field ‘wobbles’ a bit through time, so magnetic north moves around near, but not right at, the actual north pole. A compass aligns itself with the magnetic field, so it always points to magnetic north.

This is not the big problem it may seem. You can simply use magnetic north, or correct your compass bearing to coincide with true north. Your choice, but nautical charts and mariners simply use magnetic north when plotting course lines so they don’t have to bother correcting what the comass reads.

I do occasionally use topographic maps, especially for the open coast where nautical charts are generally too small scale (they are designed for sailers covering many miles well offshore) to show enough detail. The topo maps will give the magnetic deviation and you can correct for it.

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Tony Moore August 26, 2012 at 11:21 am

Great point, John, about the magnetic north wandering through time. One thing this means is that one should use an up-to-date nautical chart (or check online to see if the deviation has changed significantly for your location…changes are potentially greater the farther north you are due to the simple geometry of the situation).
Tony

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John Lull August 26, 2012 at 5:17 pm

Quite right Tony. At our latitude, it doesn’t vary by much over the course of several years. Of course it’s always best to use a fairly up-to-date chart or map. But even if the chart is 15 or 20 years old, the variation won’t be more than maybe 1 degree (I’d have to check on that, but am too lazy at the moment; I want to have a martini!). In any case, for kayak navigation, 1 or 2 degrees are well within any margin of error when using a compass at sea. I tend to round off to the nearest 5 degrees for ease of reading the compass. That’s usually close enough.

By the way, the magnetic field also reverses periodically–north becomes south. But that only happens about once every few hundred thousand years or so. Pretty often, geologically, but not so often for the time frame we live in!

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Nancy Soares August 26, 2012 at 5:40 pm

Yay, it’s martini time! Still on the Ketel One, John?

I like your idea of using a topo map. Dave had a nautical chart for the retreat this year, but it didn’t show the land features so well and we needed to find water. As it was, we were fine, but it would have been nice to have a better idea of where the streams were.

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John Lull August 26, 2012 at 8:31 pm

Of course, Ketel One all the way!

That part of the Oregon coast is a good example of an area where you can’t find a nautical chart at a large enough scale to show the detail you want. I always used a topo sheet up there. The topos show all the rocks, etc, because they are at a much larger scale. In the areas near major shipping or fishing ports, like San Francisco, you can get large scale nautical charts that show good detail.

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Moulton Avery September 6, 2012 at 1:28 pm

Two great posts on navigation in a row, John. Bravo! I know a lot of kayakers who find navigation mind-numbing, and even more who rely exclusively on GPS. I think the map & compass part has a lot to do with how the subject is presented. You have a real gift for taking the complex and making it simple, a rare and welcome talent in an age brimming with folks who excel at making the simple into something unnecessarily complex.

I’m old school and financially challenged, so I like the map & compass routine. Never had a compass break in the field, but I’ve been on a number of outings recently where GPS units carried by other paddlers have been lost overboard or simply failed.

Terrain is pretty flat here in the Chesapeake Bay area; Nancy’s point about looking behind you and your advice about keeping track of your position really rang true. You don’t have to get very far off shore for the terrain to fade into one tan blob with no features, and it’s surprising how many folks are completely stumped on the return leg of the paddle. Oddly enough, I’ve also seen this happen on lakes when following the shoreline; a lot of folks just line up like ducklings, space out, and follow the leader.

Back in the day, Brian Price and I hooked up with two paddlers for a 14+ mile crossing of the mouth of Delaware Bay. At the put-in, one of these two gives a heading that was 20 or 30 degrees East of what we had on our charts. He was also using a giant, untethered, hand-held marine compass which he kept in his lap. It would have been a bad time to play duckling.

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John Lull September 6, 2012 at 3:29 pm

Moulton, you know the “mind numbing” thing has always mystified me. To me navigation is highly interesting. But then I grew up pouring over maps of the wilderness, from the time I was a wee lad (sorry, I just finished a great crime novel by a Scottish author, Denise Mina–check her out some time!). To this day, i find magic in a map and really enjoy pondering what that cove or beach might be like, looking for the most interesting areas to paddle or hike, etc. I also grew up backpacking in the Sierras and Marble Mountains, and spent some years working as a geologist in Alaska and elsewhere. So using maps and navigating with a map and compass is second nature to me and I have a hard time imagining what it would be like not to know how to read a map or use a compass. So I guess I was lucky to learn that stuff early on.

Of course navigating on the sea in a kayak has some other unique aspects to it and I really enjoyed learning about currents and wind and how to deduce my position without being able to climb a nearby hill to get a good view of the terrain. In any case I think it’s great FUN to navigate. Not long ago, Neil Hooper & I paddled to a buoy 3 miles offshore in thick pea-soup fog, using only a compass bearing, just to see if we could find that “needle in a haystack.” Somewhat to our surprise, it worked great. We hit it dead on.

Finally, I hate being a blind follower. It scares me, to be honest. I want to know where the hell I’m going and not rely on someone else to guide me. I also think GPS units are fabulous tools, but, maybe being ‘old school’, I could never in a million years rely on an electronic device exclusively.

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Nancy Soares September 7, 2012 at 7:59 am

On the subject of being old school, I have 2 short stories about navigating in the desert which can be just as challenging as at sea. In March I was trying to find a particular hot pool among an abundance of pools at Borax Lake in the Alvord Desert. I was navigating from a hot spring book, notoriously sketchy at the best of times. I wandered around for a long time and finally resorted to holding up the book with its blurry photograph of the tufa rim of the lake and the surrounding scrub and kept moving around until my visual sighting matched the photo in the book. And there was the hot pool!

On another note, I was just at Burning Man in the Black Rock Desert. In spite of all the smoke and light pollution from the city, the stars were still visible, as well as the moon. It was interesting to me that the old-timers I was with had more trouble than I did navigating in the crowds out on the playa at night because they weren’t looking at the celestial array. I even said once, “Well, you can tell where we are by the moon.” Someone said, “But the moon moves.” Well, duh, but it moves in a predictable arc, and there’s still the north star. It cracked me up – I had visions of the moon racing erratically around the sky. But I just shut up. I knew where I was.

Hey, John, maybe we could do a post on celestial navigation. Is that something you’re up for?

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John Lull September 7, 2012 at 9:18 am

Nancy, of course celestial navigation is how sailors navigated for most of human history. I took a class on it once. It involves using a sextent, charts, and thick books of tables listing the declinations of various stars & planets for every hour of every day of the year. Not really something you’ll likely do in a kayak, except at the most basic level. Like knowing where the north star is and steering by that.

I think celestial nav is more useful for sailors crossing the ocean, well offshore. At the smaller scale we travel, and given the fact that it’s often foggy along the coast, it’s not too practical. But still good to have some idea of the layout and movement of the night sky.

I’ll work up something on crossing currents (whenever you’re ready for it), which is definitely of importance to kayakers, especially in bays, inlets, estuaries, and places like the Sea of Cortez or the inland passage of Alaska & British Columbia.

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Eric Soares September 8, 2012 at 8:10 am

Hey John, I’d love to have an article on crossing currents – I think that would be great for our readers. How about we shoot for 11/26? That should give you plenty of time.

I hear you about celestial navigation relative to kayaking, but I was thinking more along the lines of ancient Polynesians who didn’t have sextants and charts and yet were able to navigate using stars as well as the presence or lack thereof of birds, clouds, currents, even the quality and color of the water. I understand there are efforts underway to keep those old skills alive. But I agree that that’s beyond the scope of this blog. Still, I wonder how many of our readers even know how to find the north star? Just having a very basic familiarity with the night sky could be helpful.

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Moulton Avery September 8, 2012 at 4:42 pm

John, I know what you mean about maps – I just love them. State, world, topo, marine – never met one I didn’t like. I think folks get map-brain mostly on declination & the difference between taking a field bearing and a map bearing. Also contour lines. I think it has a lot to do with thinking that they should be able to instantly grok it, and I used to remind them that it was going to take a little more time and effort.

I played “follow the leader” in the outdoors one time: my first rappel. Came within a hair of going airborne 300 feet off the deck. Flatrope harness, leader says finish it with a square and back it with full hitches. I tied a granny and backed with halfs. That stuff doesn’t hold knots well, and the sucker came within a hair of completely undone when I was about 15 feet down the wall, but somehow, miraculously, caught on itself. Scared me something fierce, and I definitely learned the lesson.

I think an article on currents would be great. We don’t have very strong ones in our area, but even 2 -3 knots adds up if your crossing takes many hours.

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