The beam width of your radar is 2°. The left tangent bearing of a small island, as observed on the PPI scope, is 056° pgc. If the gyro error is 2° E, what bearing would you plot on the chart?
• Gyro error (east or west) and how it affects converting between true and gyro bearings • Difference between indicated radar bearing on a PPI and the bearing you plot on the chart • Meaning of left tangent bearing and beam width in radar plotting
• First, decide: is the 056° pgc a gyro bearing or a true bearing? How do you know from the notation? • If gyro error is 2° E, think: does Gyro best, error east make the true bearing larger or smaller than the gyro bearing? • Ask yourself whether the full 2° beam width changes the bearing you plot, or if you use just the indicated tangent bearing.
• Confirm how to convert: True = Gyro ± gyro error (decide whether to add or subtract for an east error) • Be sure whether to apply any correction for beam width, or if the given tangent bearing is already the one to be plotted (aside from gyro correction). • Check that your final plotted bearing is expressed as true degrees (no pgc, no gyro) before matching it to the choices.
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