Navigation: Ranges

When paddling, if you line up two features — artificial or natural — you have the makings of a range. A range is a type of line of position that can help you stay on course or help you find your position on the map (think of a line of position as an imaginary line that runs between you and an other point. It helps you find your position on the map). For a range, imagine a line that runs from the two lined-up features to your boat. As long as the two features remain lined up, you are somewhere along that imaginary line. If you can find those features on a map, you’re one step closer to knowing your exact location.

Natural and Man-made Ranges

You can make a range by lining up any two features, including natural or artificial. For example, “Range 1” is a line drawn from the mark at the opening of Marquette Bay and the Goose Island Shoal mark. Once you paddle to a point where those features line up, you’re on that line. Other example ranges: You might use a buoy and a natural feature, like shown by “Range 2”. Or, you might use two natural features, like the end of Goose Island and the peninsula in “Range 3.” If you’re using a range to keep a correct course, you might use two trees, the peak of a hill and a shoreline feature. If they stay lined up, you’re paddling a straight course. Basically, anything that stands out in your mind and lines up can make a range. For example, if you’re surfing and you know where the waves are breaking, you might make a range using two trees. When the trees line up, you know you’re in the “line-up.”

Determining a Line of Position

Once you’ve identified a number of ranges on a map, you can use those as lines of position. Once the two features line up, you’re on that line. If you can line up two lines of position, then you have a fix, which gives you a pretty close indication of your position on the map. Think: “X” marks the spot. For example, “Range 4” lines up two marks and “Range 5” lines up a mark and the tip of Government Island. If you’re on “Range 4,” you could be at point “a,” “b” or anywhere on that line. If you line up the features on “Range 5,” you might be at point “c” or “b” or anywhere else on that line. If both “Range 4” and “Range 5” line up, you have a fix and are at point “b.”

An other way to use ranges is to help you determine your progress while paddling along. Once you hit the range, you know how far you’ve come since the last range you took. For example, if you’re paddling from the top right to the bottom left of this map (heading southwest) parallel to “Range 4”, you might make a range from the G “5” mark to the tip of Strongs Island. As you paddle you pass “Range 5.” You can then measure the distance you’ve come on the map. The distance scale isn’t shown, but the distance is about 2 miles. A simpler way to think about this example is that once you line up the features on “Range 5,” you know that you’re off the point of Government Island.

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Exercise: There are many ranges on these two images. See if you can find some that I didn’t mark.

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Ranges Help Keep Course

If you know your course and want an easy way to keep it. Line your kayak up with your course bearing and look for two features in front of you that you can line up. If you can’t find two in front of you, find one in front of you and one behind you. As long as these features stay lined up, you stay on your course. If they don’t, then something is pushing you off-course — maybe current or wind. If the front feature is left of the rear feature, you’ve drifted to the right. If the front feature is right of the rear feature, you’ve drifted to the left. To experience this now, line up two coffee mugs. Move to the left and then to the right. Watch what happens to the cups. While paddling, you might need to adjust your heading and ferry your course if it’s absolutely important that you stay on the range.