1. What is Magnetic Variance?

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

2. How Does the Calculator Work?

The calculator uses the magnetic variance equation:

Where:

• \( X \) — North component of the magnetic field (in nanoteslas, nT)
• \( Y \) — East component of the magnetic field (in nanoteslas, nT)

Explanation: The arctangent function calculates the angle whose tangent is the ratio of the east component to the north component of the magnetic field.

3. Importance of Magnetic Variance Calculation

Details: Accurate magnetic variance is crucial for navigation, compass calibration, and various scientific applications where precise directional measurements are required.

4. Using the Calculator

Tips: Enter the north (X) and east (Y) components of the magnetic field in nanoteslas (nT). Both values must be valid numbers.

5. Frequently Asked Questions (FAQ)

Q1: What's the difference between magnetic variance and magnetic inclination?
A: Variance refers to the horizontal angle between magnetic and true north, while inclination refers to the vertical angle between the magnetic field and the Earth's surface.

Q2: How often does magnetic variance change?
A: Magnetic variance changes gradually over time, typically a few minutes of arc per year, though this varies by location.

Q3: Where can I find current magnetic field components?
A: National geophysical surveys and organizations like NOAA provide current magnetic field data for different locations.

Q4: What's the range of possible variance values?
A: Magnetic variance can range from -180° to +180°, though most locations have values between -30° and +30°.

Q5: Why use atan2 instead of simple atan?
A: The atan2 function properly handles all quadrants and avoids division by zero, making it more robust for this calculation.