by Tsunami Ranger John Lull
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
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.
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.
With the course line(s) plotted, your chart has the information you’ll need to navigate using a compass.
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.
“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 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.