1. What is Great Circle Distance?

The great-circle distance is the shortest distance between two points on the surface of a sphere, measured along the surface of the sphere. For Earth, this represents the shortest path between two locations (as the crow flies).

2. How Does the Calculator Work?

The calculator uses the haversine formula:

Where:

• \( R \) — Earth's radius (6371 km)
• \( \phi_1, \phi_2 \) — Latitude of point 1 and point 2 (in radians)
• \( \Delta\lambda \) — Difference in longitude between two points (in radians)

Explanation: The formula calculates the central angle between two points on a sphere using their latitudes and the difference in their longitudes.

3. Importance of Great Circle Distance

Details: Great circle distance is essential for navigation, flight planning, and telecommunications. It provides the most accurate measurement of distance between two points on Earth's surface.

4. Using the Calculator

Tips: Enter coordinates in decimal degrees (e.g., 40.7128 for New York). Latitude ranges from -90 to 90, longitude from -180 to 180. Select desired output unit (km or miles).

5. Frequently Asked Questions (FAQ)

Q1: How accurate is this calculation?
A: The calculation assumes a perfect sphere. Earth is an oblate spheroid, so actual distances may vary by up to 0.3%.

Q2: Can I use this for very short distances?
A: For distances less than 20km, planar approximation might be sufficient, but this formula works for all distances.

Q3: What coordinate system should I use?
A: Use decimal degrees (WGS84) for best results. Degrees-minutes-seconds should be converted to decimal first.

Q4: Why is the distance not the same as driving distance?
A: Great circle distance is the straight-line distance through Earth, while driving distance follows roads and terrain.

Q5: How does altitude affect the calculation?
A: This calculation ignores altitude differences and computes surface distance only.