1. What is Magnetic Variation?

Magnetic variation (also called magnetic 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 World Magnetic Model (WMM) developed by NOAA:

Where:

• \( \text{latitude} \) — Geographic latitude in degrees (-90 to 90)
• \( \text{longitude} \) — Geographic longitude in degrees (-180 to 180)
• \( \text{altitude} \) — Height above sea level in meters
• \( \text{date} \) — Year for which to calculate the variation

Explanation: The WMM is a spherical harmonic model of Earth's magnetic field that accounts for both spatial and temporal variations.

3. Importance of Magnetic Variation

Details: Magnetic variation is crucial for navigation, aviation, surveying, and any application requiring precise directional information. Ignoring it can lead to significant navigation errors.

4. Using the Calculator

Tips: Enter latitude (-90 to 90), longitude (-180 to 180), altitude in meters, and the desired year. The calculator will estimate the magnetic variation for that location and time.

5. Frequently Asked Questions (FAQ)

Q1: How often does magnetic variation change?
A: The WMM is updated every 5 years to account for secular variation in Earth's magnetic field.

Q2: What's the difference between magnetic variation and magnetic inclination?
A: Variation is the horizontal angle between true and magnetic north. Inclination is the vertical angle between the magnetic field and the horizontal plane.

Q3: Where is magnetic variation zero?
A: Along the agonic line where magnetic north and true north align. This line moves over time.

Q4: How accurate is the WMM?
A: Typically accurate to within 30 minutes of arc for declination, with accuracy decreasing near the poles.

Q5: Why does altitude affect magnetic variation?
A: The magnetic field strength decreases with altitude, though the effect on declination is generally small.