Navigation: Fixes and Triangulation

When lost or slightly misplaced while kayaking or canoeing, if you have a view of a couple of landmarks you can get a fix, which is the navigational term for finding an “X” that marks the spot. The “X” is your location. The process is a quick and easy way to find your location. For a more exacting needs, finding your location with triangulation involves only one extra step.

Getting a Navigation Fix

First, find a line of position, which is a line that runs from a landmark to your position. You can take a bearing with your compass or find a range to get a line of position. To get a line of position with a bearing, take a bearing with a compass to a landmark, find the landmark on your map and draw a line from the landmark on a reverse bearing (account for variation) out towards your position. A reverse bearing is 180 degrees from your bearing. Extend the line for a length you estimate you’re away from the landmark. You are somewhere on the line. With a plastic map case and a grease pen, you can draw directly on your map or chart and easily wipe it off later.

To get a fix, draw a second line of position from another landmark. Your position is near where the two lines cross. Try to find a second line of position that crosses the first at a 90 degree angle for greater accuracy. Also, because of drift, the faster you take your bearings and find your fix the more accurate it is.

With a baseplate compass, you don’t need to figure out the back bearing. Take a bearing with the compass, adjust it for any variation, then place it on the map with the arrow pointed towards the landmark. Align one of the long edges of the compass with the landmark, and then align the north-south lines inside the compass’ housing with the north-south lines on your chart or map. Draw a line along the side of the compass touching the landmark.

Triangulation

For triangulation, draw a third line of position. The three lines of positions cross and form a triangle. Your kayak or canoe is somewhere inside the triangle. This gives you a more accurate position. Often a fix gives you good-enough approximation that you can look around, reference a nearby landmark and more accurately determine your exact location quicker than making a third line of position, but if you need accuracy, it’s hard to beat triangulation.

Example of a Navigation Fix and Triangulation

You’re paddling somewhere north of York Island in the Apostle Islands (shown in the image at the top), and you want to know your exact position, so you decide to get a fix. The first bearing you take reads 36 degrees from the G “1” buoy off of the York Island Shoals. You draw the line backwards from the buoy using a back bearing. You now know that you’re somewhere along this line of position. Second, you take a 290 degree bearing off the R “2” buoy. You draw that on your chart. You now know that you’re somewhere near where the two lines cross. For a more exact position, you take a third bearing of 150 degrees to the northeastern point of York Island. Drawing the line on the chart gives you a triangle. You are somewhere inside the triangle.