Quick Answer
When navigating in urban areas, rely on true north when you're using a compass without knowing the local magnetic declination, or when you've calculated and accounted for it, and need to align with a specific point, such as finding a landmark or direction.
Magnetic Declination and Compass Use in Urban Areas
In urban areas, magnetic declination can be significant due to the presence of ferromagnetic materials like steel skyscrapers and roads. This can cause your compass to point in a direction that’s different from true north. If you’re using a compass without knowing the local magnetic declination, it’s best to rely on true north to get an accurate bearing.
Calculating and Accounting for Magnetic Declination
Understanding and accounting for magnetic declination is crucial when using a compass in urban areas. You can calculate the declination by using a declination chart or app, or by consulting with a local expert. For example, in New York City, the magnetic declination is approximately 11° east. If you’re using a compass to navigate, you’ll need to adjust your bearing by this amount to get an accurate reading.
True North and Compass Use
When relying on true north in urban areas, use your compass to align the direction-of-travel arrow with the magnetic needle. Then, use a protractor or angle-measuring tool to calculate the angle between the direction-of-travel arrow and true north. This will give you your bearing, which you can use to navigate. For example, if you’re trying to find a landmark that’s due north of your current location, use your compass to align the direction-of-travel arrow with true north, and then use the protractor to calculate the bearing.
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