Sea Kayak Navigation: Plotting Your Position With A Compass

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In an earlier post, we discussed how to use a chart and compass to find a compass bearing we could follow to a desired destination. But all those techniques for heading somewhere new require us to know where we are now. As any kayaker who’s ever done a longer crossing or paddled along a featureless shoreline can confirm, it’s easy to lose track of your precise location. How do we find it again? 

First, a quick detour into a concept called a Line Of Position (LOP). You’ve almost certainly used LOPs before, even if you didn’t call them LOPs. If you were wandering around a city (for example, Vancouver, British Columbia) with a paper street map, you might have known you were somewhere on Granville Street, but not sure where along Granville. So you walked down to the next corner and checked the signs for the cross street. Finding it was Broadway, you now knew your exact location: the intersection of Granville and Broadway. Each of those streets served as one LOP for you. Where the two LOPs intersected was your location.

A section of roadmap showing the intersection of Broadway and Granville in Vancouver, British Columbia. Demonstrating the concept of Lines Of Position.
Granville Street is one Line Of Position. Broadway is a second Line Of Position. Where they intersect is your location. See, you’re already a navigator!

To determine our location when sea kayaking, we do exactly the same thing: we find the intersection of two or more LOPs. The only difference is that we use lines other than streets as our LOPs.

Even for novice kayak navigators, there’s one Line Of Position that’s so obvious you’ve probably used it without even thinking about it: the shoreline. (Yes, most shorelines are curvy and crinkly rather than straight. But there’s no requirement that every Line Of Position be a straight line. In my hometown of Vancouver for example, Kingsway Road has lots of jinks and bends, but I can still use it to clearly define a position such as “the intersection of Kingsway and Broadway.”)

Bendy LOPs? No problem: where they intersect is still your position.

So, if we only ever intend to navigate along shorelines, why would we ever need a second LOP?

Imagine you and I and several friends are kayaking close alongside the southwest shore of North Pender Island, admiring the undersea flora on the rock wall and petting the passing Orca. Distracted by all this merriment, we’ve lost track of how much time we’ve spent paddling vs drifting. Plus, the tricky currents on this coast have sped us up or slowed us down unpredictably. So now all we’re sure of is that we’re somewhere between Boat Nook and Smuggler’s Nook. We need a second LOP to show us exactly where between those points.

A section of marine chart, showing the lines of magnetic North drawn in with red, to allow plotting Lines Of Position without adding or subtracting for compass variation.
A section from CHS Chart #3441. Look for Canoe Rock (below the purple compass rose) and Pelorus Pt (on the right/East side of Moresby Island). The red lines I’ve drawn in point to magnetic North, 16° East of truth North. (Why 16° East? The purple compass rose shows true North, magnetic North as of 2005, and a predicted change in the magnetic variation of 8’ Westward annually. So in in the 18 years since 2005, the variation is predicted to have reduced by 2° 24’ (18 years x 8’ = 144’ or 2° 24’). The variation in 2005 was 18 1/2° or 18° 30’. Subtracting 2° 24’ from that gives us 16° 6’ East. This matches pretty closely with the 15° 46’ East predicted for this area by the online declination calculator. We can round either figure to 16° East for practical purposes.)

To lay out a second LOP, we need to take a compass sighting (AKA a bearing) from any clearly identifiable location shown on the chart and visible from where we are in the real world. A lighthouse, the tip of a cape, one side of a known island, or a distinctive mountain peak would all be excellent options. 

Looking out to sea from Pender Island, we find a highly distinctive landmark to take a bearing from: the red-and-white marker on Canoe Rock. Even better, it’s at roughly a right angle to the shoreline. (It’s a good habit to pick your landmarks so that your LOPs meet at as near to right angles as possible; this creates a much clearer intersection point than sharp acute angles or almost parallel obtuse angles.)

Taking a bearing from a real-world object (in this case, the orange thingie representing the marker on Canoe Rock) using a hiker’s/orienteering compass. Step 1. Holding the compass as level as possible, aim the Direction Of Travel arrow towards the landmark. Pro tip: this is much easier and more accurate if your body is facing the landmark. Which means your boat should also be pointing in at least the general direction of the landmark. Notice that at this time, the compass bezel dial is in a random direction relative to the magnetic compass needle, with the N (for North) on the bezel not aligned with the red needle tip. 
Taking a bearing from a real-world object using a hiker’s/orienteering compass, Step 2. While keeping the Direction Of Travel arrow aimed at the landmark, twist the bezel dial until the meridian lines in the bottom have put “Fred in the shed” — that is, the red box on the bottom of the bezel is enclosing the red half of the magnetic needle, and the N on the bezel is directly in front of the red needle tip. Read off the degrees at the Read Bearing Here indicator. In this case, the bearing to Canoe Rock is 224°. (BTY, if this whole process feels exactly the same as taking a bearing to a visible landmark you want to paddle to following a compass course, that’s because…it is!)

Great. We have our bearing off Canoe Rock. So now what? So now, we’re going to transfer that bearing into an LOP on our chart.

A section of marine chart with a hiker's compass, bezel parallel to the lines of magnetic North. Showing how to draw a Line Of Position on a chart.
Using a hiker’s compass to transfer a bearing onto a chart as an LOP. We keep the bezel dialed to 224°, from when we “shot” our bearing to Canoe Rock. Keeping the meridian lines on the bottom of the compass bezel as parallel as possible to the red magnetic North lines on the chart, we put one edge of the compass baseplate on the Canoe Rock landmark on the chart. That baseplate edge is now a Line Of Position. Where that LOP intersects the shoreline is our location. In this case, the baseplate doesn’t quite reach to Pender Island, so we extend the LOP by eye and pencil it in. (Notice that we don’t care about where the compass needle is pointing now: we’re just using the compass bezel and baseplate as a protractor.)

Woot! We are unlost! We are right where the shoreline (the first LOP) and the bearing from Canoe Rock (the second LOP) meet. High fives everyone! 

BUT…

We took that compass bearing with a hand-held land compass from the cockpit of a kayak rocking in the waves (landing to take the bearing wasn’t an option on the cliffy shores). And we extended that LOP by eye from where we ran out of compass baseplate. So there have been lots of opportunities for errors to creep in. How can we cross-check our apparent position? By determining a third LOP.

Happily, our pod of paddlers includes the excellently-equipped Greta Geerweenie, so we can not only shoot an entirely separate landmark, we can do so using a more accurate instrument. Because Greta’s kayak boasts a deck compass, aligned with the keel line of her kayak. So to take a bearing, she simply aims the bow of her boat toward her chosen landmark (Pelorus Point on the east side of Moresby Island), and reads the bearing in degrees at the lubber line.

A model kayaker with a real, full-sized marine compass pointing towards a marker. Showing how to take a bearing on a landmark with a deck-mounted kayak compass.
Taking a bearing with a deck-mounted marine compass. With the kayak pointing towards the real-world landmark (the orange thingie now representing Pelorus Point), we read the bearing directly from the black “lubber line.” In this case, it’s 172°. (No bezel twisting required. Because instead of the needle on a hiking/orienteering compass, a marine compass has a floating, degree-marked dial that rotates to line up with local magnetic North.)

But Greta’s opportunities to flaunt her superior gear don’t end with the deck compass. Now it’s time to transfer the bearing she shot onto the chart as that third LOP. Rather than roughing it with the hiker’s compass, she whips out her modified Davis Protractor, complete with String™ that extends much further than the baseplate on a hiker’s compass.

A chart with string-added Davis Protractor. Showing how to use the string as a Line Of Position to determine your location based on a compass bearing to a known landmark.
Using a string-equipped Davis Protractor to transfer a bearing onto a chart as an LOP. Position the protractor’s centre point over the landmark we took the bearing on (Pelorus Point). Pivot the protractor until its North-South grid lines are parallel to the red magnetic North lines on the chart. Pull the string taut across the degree reading we got with the compass (172°) on the outside edge of the protractor. Where the string intersects the shoreline is our location. Reassuringly, it’s pretty much the same place as the LOP from the first landmark showed us. (And remember how we said we don’t care about where the compass needle is pointing for this step? The Davis Protractor doesn’t even have a compass needle to distract us!)

We won’t always be paddling with a Greta Geerweenie. But we still can (and should) cross-check our plotted position wherever possible by shooting at least two landmarks as bearings and bringing them down onto our chart as LOPs, even if we’re only using a humble hiker’s compass for everything. It’s also true that in the real world, our multiple LOPs won’t usually intersect with the suspiciously perfect agreement they have in this story: typically they’ll form a triangle. You’ll know you’re somewhere inside that triangle, and as long as it’s small enough, it will be good enough for navigation purposes.

A PLOT TWIST!

Clever readers (which is all of you, of course) will have realized something: once we’ve intersected two or more LOPs based on compass bearings, we don’t need the shoreline LOP anymore to know where we are. That’s exactly how bigger, deeper boats, who need to stay further from the shore than kayaks, do it. And exactly how you can do it as you graduate from simple shoreline paddling to longer crossings. There are even other compass-free LOPs you can use when away from the shore. But we’ll save those for another post.

Sea kayak safety: the parallel rescue

Plenty of sea kayakers know the bow rescue – a technique where the rescuer presents the bow of their kayak to a capsizee, so the unfortunately inverted paddler can hip flick back up using the bow for support. There are many Youtube videos showing it, and it’s taught in Paddle Canada and other sea kayaking courses.

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Electric Pump for Sea Kayak, Mark III

For several boats now, I’ve been outfitting my sea kayaks with electric pumps. (My reasons are explained in the first part of this posting.)

an electric pump in a sea kayak

So I’ve fitted my new-to-me Valley Etain with an electric pump as well. The overall design is pretty similar to my last pump, with a waterproof Pelican battery box designed to let me run the system on either 12 rechargeable AA batteries or 8 alkaline AAs. A stretchy Velcro strap and a pair of stainless steel footman’s loops hold the battery pack in place against the bulkhead at the back of the cockpit.

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Fit To Be Tried: New Sea Kayaking Gear

paddlers admire a table of sea kayak clothing and equipment

Coffee with a gear buffet

There are a few perks to being a sea kayak Instructor/Guide. Like being invited to join a focus group run by Mustang Survival. In Canada, Mustang has long been a go-to brand for recreational boaters, commercial fishers and racing sailors. But, with the exception of a manual inflation vest that’s popular with paddlers who can’t find a foam PFD that fits their body shape (or who just find foam PFDs too warm), Mustang’s products haven’t been top-of-mind in the sea kayaking market. They’re gunning to change that. Which is why I found myself, along with three fellow instructors, doing dawn patrol on a crisp, sunny fall morning.  Continue reading

I Wanna Roll Like A Girl

Back in the day, I had a bombproof kayak roll. But gradually, I fell out of the habit of practising it. When I first abandoned whitewater and surf paddling in favour of exclusively ocean kayaking I kept it up. But over the years, I persuaded myself it wasn’t really essential for sea kayaking and probably wouldn’t work anyway with my sail on the boat. Besides, my brace worked fine (except when it didn’t.) Somewhere along the line, I convinced myself that age made it unlikely I could recapture my roll.

A kayaker surfs a breaking wave

Displacement Hull Boat? Check. Wood Paddle? Check. Chunky PFD? Check. This must be me, surfin’ the 90s.

But this year, one of my personal and professional goals is to regain my roll. And to do it like a girl.

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‘ Yak Hacks: Raise Your Light High For Night Paddling

Off-the-shelf kayak lights are an excellent way to increase safety when night paddling. By raising your light a few feet above the deck you can ensure it remains unblocked by your body and visible through the full 360. Plus, it won’t nuke your night vision by shining directly in your eyes. Continue reading