At 0812, you are on course 132°T. The standard magnetic compass reads 135°. What should you conclude?
• Difference between true course and standard magnetic compass course • How variation and deviation relate true, magnetic, and compass headings • What you can and cannot conclude from one single compass observation
• First, think about whether you know the variation and the expected deviation for this heading. Without those, what can you safely say? • Ask yourself: does a 3° difference between true and compass automatically mean the compass is wrong, or could it be normal? • Consider what information you would need to say anything about deviation changing with latitude (going south). Do you have that information here?
• Verify whether any charted variation at the vessel’s position has been given in the question (or not). • Check if the question gives you the deviation table values for heading 132°T or 135°C; if not, what does that imply about answers that rely on that table being right or changing? • Confirm what the standard magnetic compass actually measures (magnetic direction plus deviation), and whether this single reading alone proves a problem with the compass or charted data.
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