Getting Disciplined: Open Water Navigation
By Ian Adamson
"Bring her round two points to starboard and heave to on the weather shore until the start of the ebb, Mr. Mate." That's mariner-speak for "let's go over there to the right and rest behind that island until the tide changes." Regardless of the language you use to communicate your navigation on the water, there are a few basic rules that will keep you on course and out of trouble.
1) Feature recognition. The biggest challenge for most people unfamiliar with open water navigating is being able to recognize features and maintain a straight line across the ground (as opposed to through the water, which I will explain later). Trouble with feature recognition is due mainly to difficulties estimating distance and shapes, which is not an easy thing to do without experience. In general, you can see much greater distances over water than on the land, because the terrain is essentially flat. As a result a distant object like an island can appear quite close, when in reality it may be many miles away. If the water is rough, your vision can be obscured by spray and swell, and it might be very difficult making out smaller features until you are quite close. Usually, your horizon is about a mile away if you are sitting in a kayak and looking at something at water level. The higher you are off the water the further your horizon actually is. If you are looking at an object that is not at water level, which is generally the case, then the taller it is the further away you can see it. This is due to the curvature of the earth, and can be complicated by fog, mist, spray, reflection, sea conditions and distortion at the horizon line.
2) Distortion. You also need to understand how distortion on the waters surface changes and obscures objects. As you approach your destination over a large stretch of water, an island for instance, it will first appear as a small dot hovering over the surface. This strange phenomenon is due to the refraction of light as you look through it around the curve of the earth's surface, somewhat like looking through the edge of a very large lens. As you get closer, the dot becomes a blob, with the edges curving in and under towards the water.
The challenge here is to understand how a shape on a map, which is drawn as though you are looking at it from above, will appear as you look at it from a very low vantage point from the side. If you imagine your destination submerged and slowly rising up through the water, you will have a good idea of how it will appear as you paddle towards it. With this in mind, anything you are aiming for will probably be close to water level so you will have to identify adjacent features first, a building, hill or other large object.
3) Drift. Drift can be a big problem during ocean crossings since you often lack visual references and wind, waves and current have a big effect on your course. Current can be invisible and wind and wave action insidious, so you need to apply close attention to these influences. A few degrees or a small cross current are all it takes to put you several miles away from your destination over several hours paddling, say crossing Lake Michigan or between islands in the South Pacific.
The method used to accommodate wind drift and current is called dead reckoning, possibly because a mistake by ancient mariners may have been deadly. In dead reckoning you need to guess the effect of wind (leeway for those nautically inclined) and current. Current is generally marked on nautical charts (marine maps), but you have to guess at leeway, which can be considerable in heavy conditions. A very rough rule of thumb for leeway in a sea kayak is 1 knot (roughly 1 mph) per every 10 knots of cross wind. But this can vary wildly depending on wave action, wind power and hull shape. If you are serious about your navigation and paddling, you will have to figure out for yourself, how you're set up performs in various conditions. So get out there and get wet!
Ian Adamson is a record-setting paddler and navigator for Elite Adventure Team.
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