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Lesson 01 - Obtaining Your Position Though Landmark Bearings With some simple tools, you can easily plot your position if you recognize one or more navigational aids. All you need is a chart, parallel rules (or navigation triangles, if you prefer), a pencil, and a hand-bearing compass. To plot your position, take a bearing on the first navigational aid or landmark with your hand-bearing compass. On your chart, use the parallel rules to draw a line from the navigational aid along the chart, using the bearing to the aid as the compass course to the navigational aid. (fig.1)  Repeat the process with the second navigational aid. The point at where the two lines intersect is your boat's position. (fig. 2)  To increase accuracy, you should use navigation aids that are approximately 90 degrees apart from each other. If you have bearings on two navigation aids that are close to each other, you allow too much room for error when plotting your position (fig. 3). Using more than two navigation aids also increases accuracy; you should try to use at least three.  Finally, you may use this technique with other navigation tools, such as radar. If you are passing near two islands, you may take bearings on the islands using your radar, just like you would with a hand-bearing compass and navigation aids. |
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