Kayak navigation can be complicated. But there’s one aspect of navigation and “dead reckoning” that’s relatively simple yet pretty important once you understand the concept.
Let’s say you’re out there kayaking on a large lake or in the ocean. Off in the distance you spot a boat under power (or sail) and it looks like the two of you are going to cross paths. But how can you tell if you’re on a collision course? The simple yet practical way to find out is called “Angle to the Bow,” also known as “constant bearing, decreasing range.”
Here’s how it works.
1. First of all, if you see a large boat or ship approaching, hold your course.
2. Shoot a bearing to the other boat. If you have a hand-held compass, great. Use it to sight the bearing to the other boat. However if you’re like me you don’t always carry a hand-held compass because you have a deck-mounted compass or because you feel you don’t always need a compass in familiar waters. No worries. You can achieve results without a compass. In that case, judge the angle to the other boat by lining it up with a reference point on your kayak’s front deck such as the edge of your hatch cover or a deck line fitting.
3. Keep paddling forward in the same direction for a minute or two, and then take the bearing again to the approaching boat.
4. If the angle to the bow of the other boat is increasing, it means you will pass in front of it. If the angle is getting smaller, it indicates you’re on course to pass behind it. If the second bearing is the same as the first, or if the approaching boat is still lined up with the reference point on your deck, and nothing else has changed, (that is, you and other boat have not changed course or speed) then you know you’re on a collision course. Or at least it will be a close call.
5. Watch the other boat carefully and slow down or stop if you need to. Remember, he (or she) may not see you. Also, it’s been my experience that powerboaters often underestimate how fast sea kayaks actually travel.
But wait, there’s more.
If you can see land behind the boat you’re converging with, you can tell if a collision is in your future without using a compass or other reference.
1. Again, hold your own course steady.
2. Watch a feature of the distant land near the bow of the crossing boat, and keep watching.
3. If that land feature disappears behind his bow, he’s gaining land on you and will cross you.
4. If the land feature draws ahead of his bow, as if he’s falling behind on the land from your perspective, then you will cross in front of him.
5. If the land feature stays right where it was on his bow when you first started looking at it, then you’re on a potential collision course. If the other guy does not change course, you may need to stop or slow down.
The Angle to the Bow technique works best when you’re dealing with large boats that don’t frequently change course and speed. It’s not as useful when you’re trying to avoid smaller powerboats and sailboats that are tacking or otherwise changing course and speed often.
When I teach sea kayaking I find that even some seasoned paddlers have never heard of this technique. Try it the next time you’re paddling.
Reference: “Collision Course with a Crossing Boat? How to Know” by Doug Larson. Boat.com. April 10, 2013
This is good information and i appreciate your sharing it – however, the formatting is funky and makes it hard to read. I would suggest not padding text around the pictures, or if you must do so pad the text to the left where people are more likely to expect it.
Thanks for calling this to my attention. Somehow the formatting went funky on me. I’ll attempt to correct it.
I am surprised that the technique of watching the land behind the other boat is recommended, as it doesn’t work. I think that it’s a mis-extrapolation of using ranges on non-moving objects, but it simply doesn’t work if the other object (the other boat) is moving.
Here is a sequence of diagrams of a collision course that demonstrates the problem (and the solution)
https://jjbong.smugmug.com/Other/Ranging-Misconception/n-Mh4gdW/
Note that on the collision course, the land reference behind the other boat moves, which is not what the technique above says.
On the other hand, the bearing to the other boat remains constant as the distance decreases, which is a sure sign of a collision. You do this with radar, and you can approximate it by lining up the other boat visually to a reference on the side of your boat (a stanchion, maybe, or just a point you can remember). If that reference point does not move as the other boat gets closer, you are on a collision course.