Daily Magnetic Variation Calculator Based On WMM

World Magnetic Model (WMM) Calculation:

\[ \text{Magnetic Variation} = f(\text{latitude}, \text{longitude}, \text{altitude}, \text{date}) \]

Latitude:

degrees

Longitude:

degrees

Altitude:

meters

Date:

year

Magnetic Variation:

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1. What is the World Magnetic Model?

The World Magnetic Model (WMM) is a joint product of the United States' National Geospatial-Intelligence Agency (NGA) and the United Kingdom's Defence Geographic Centre (DGC). It represents the magnetic field of Earth and is used to calculate magnetic variation (declination) at any point on the globe.

2. How Does the Calculator Work?

The calculator uses the WMM to compute magnetic variation:

\[ \text{Magnetic Variation} = f(\text{latitude}, \text{longitude}, \text{altitude}, \text{date}) \]

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 uses spherical harmonic coefficients to model the Earth's magnetic field, accounting for both spatial and temporal variations.

3. Importance of Magnetic Variation

Details: Magnetic variation (declination) is crucial for navigation, as it represents the angle between magnetic north and true north. Accurate calculation is essential for aviation, marine navigation, and land surveying.

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 in degrees.

5. Frequently Asked Questions (FAQ)

Q1: How often is the WMM updated?
A: The WMM is updated every 5 years to account for the changing nature of Earth's magnetic field.

Q2: What is the typical range of magnetic variation?
A: Variation ranges from -30° to +30° depending on location, with extreme values near the magnetic poles.

Q3: Why does altitude affect magnetic variation?
A: The Earth's magnetic field strength decreases with altitude, though the effect is relatively small for typical aircraft altitudes.

Q4: How accurate is this calculator?
A: Using the official WMM, accuracy is typically within 30 minutes of arc (0.5°) for declination.

Q5: Can I use this for navigation?
A: For critical navigation, always use official, certified tools and charts. This calculator is for informational purposes.