Quick Answer
Declination varies significantly by region, with some areas experiencing variations of up to 20 degrees between magnetic and true north. In the Northern Hemisphere, declination is generally westward, while in the Southern Hemisphere, it's eastward. Understanding local declination is crucial for accurate navigation.
Understanding Declination
Declination is the difference between magnetic and true north, and it’s essential to know the local value for accurate navigation. You can find declination charts online or in navigation guides for your specific region. In the United States, for example, declination ranges from 0 to 20 degrees, with some areas experiencing variations of up to 20 degrees between magnetic and true north.
Measuring Declination
If you don’t have access to a declination chart, you can measure it using a compass and a map. Find a known landmark, such as a city or a mountain, and its magnetic bearing using a compass. Then, measure the true bearing to the same landmark using a map. The difference between the two bearings is your local declination. For example, if a landmark is 270 degrees magnetic and 252 degrees true, your declination is 18 degrees east.
Calculating Declination
You can also calculate declination using a formula or an online tool. The formula involves the latitude and longitude of your location, but it’s generally more accurate to use a pre-calculated chart or a tool specifically designed for this purpose. Keep in mind that declination can change over time due to the movement of the Earth’s magnetic field, so it’s essential to update your knowledge regularly.
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