1. What is Magnetic Variation?

Magnetic variation (or declination) is the angle between magnetic north and true north. It varies by location and changes over time due to movements in Earth's magnetic field.

2. How Does the Calculator Work?

The calculator uses the NOAA World Magnetic Model (WMM):

Where:

• Latitude — Geographic coordinate (-90° to 90°)
• Longitude — Geographic coordinate (-180° to 180°)
• Altitude — Height above sea level in meters
• Date — Year for which to calculate the variation

Explanation: The WMM is a joint product of NOAA and the British Geological Survey that models Earth's magnetic field.

3. Importance for Car Navigation

Details: While modern GPS systems automatically account for magnetic variation, knowing the local variation can help when using traditional compass-based navigation in cars.

4. Using the Calculator

Tips: Enter your GPS coordinates (latitude/longitude), altitude (if known, otherwise use 0), and the current year for most accurate results.

5. Frequently Asked Questions (FAQ)

Q1: How often does magnetic variation change?
A: The WMM is updated every 5 years, with small changes occurring continuously.

Q2: Why is altitude important?
A: Earth's magnetic field strength decreases with altitude, affecting the variation calculation.

Q3: How accurate is this calculator?
A: Using the official WMM, accuracy is typically within 30 minutes of arc (0.5°).

Q4: Do I need to account for magnetic variation in my car?
A: Most modern navigation systems handle this automatically, but it's good to know for compass use.

Q5: Where can I find my exact coordinates?
A: Use a GPS device or smartphone mapping app that shows latitude/longitude.