1. What is Magnetic Variation?

Magnetic variation (or declination) is the angle between magnetic north and true north. This calculator uses the World Magnetic Model (WMM) to estimate magnetic variation for locations in the UK based on latitude, longitude, altitude, and date.

2. How Does the Calculator Work?

The calculator uses the 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 variation

Explanation: The WMM accounts for changes in Earth's magnetic field over time and space.

3. Importance of Magnetic Variation

Details: Accurate magnetic variation is crucial for navigation, aviation, surveying, and compass use. In the UK, variation changes by about 0.1° per year.

4. Using the Calculator

Tips: Enter coordinates in decimal degrees (e.g., 51.5074° N, 0.1278° W for London). Altitude affects results slightly (especially for aviation). Date should be between 1900-2100.

5. Frequently Asked Questions (FAQ)

Q1: How accurate is this calculator?
A: Using the official WMM, accuracy is typically within 0.5° for the UK, though local anomalies may exist.

Q2: How often does magnetic variation change?
A: The WMM is updated every 5 years. Annual change in UK is approximately 0.1° East per year.

Q3: Why does altitude matter?
A: The magnetic field varies with height, especially important for aviation applications.

Q4: What's typical variation in the UK?
A: Currently ranges from about 0° in eastern England to -4° in western Scotland.

Q5: Can I use this for navigation?
A: For critical navigation, always consult current official charts which include magnetic variation.