Quick Answer
If your compass and map don't align, first try to identify the discrepancy and adjust your map or compass accordingly. Check for declination, magnetic variation, and ensure your compass needle is not magnetized by nearby metal objects. Rotate your map or adjust your compass direction.
Checking for Declination
Declination occurs when a compass needle diverges from its magnetic axis due to the Earth’s magnetic field variations. In the United States, declination ranges from 0 to 20 degrees. To check for declination, consult a declination chart or use a smartphone app like Magnetic Field or Declination. Compare the declination value for your location to your map’s grid north. If there’s a difference, adjust your compass direction by the same amount in the opposite direction.
Using a Magnetic Variation Map
A magnetic variation map indicates the difference between magnetic north and true north. These maps are often included in topographic maps or found online. To use a magnetic variation map, locate your position and note the magnetic variation for that area. Rotate your map so that the magnetic variation line aligns with your compass direction. This ensures your map and compass are aligned.
Avoiding Compass Interference
Compass needles can become magnetized by nearby metal objects, causing inaccurate readings. To avoid this, keep your compass away from metal objects like cars, buildings, and tools. If you suspect your compass is magnetized, try demagnetizing it by holding it near a magnet or by shaking it vigorously.
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