Geodetic Calculator
Compute great-circle distance, initial/final bearings, midpoint, and destination coordinates on a spherical Earth model (WGS84 mean radius approximation).
1) Distance & Bearing Between Two Coordinates
2) Destination Point From Start, Bearing, and Distance
What Is a Geodetic Calculator?
A geodetic calculator is a tool used to solve navigation and mapping problems on the curved surface of the Earth. Instead of treating Earth like a flat plane, geodetic calculations use spherical or ellipsoidal geometry to produce realistic distances, headings, and coordinate results. This matters a lot for aviation, marine routes, GIS analysis, surveying, and any long-distance planning.
The calculator above supports two of the most common geodesy workflows: the inverse problem (given two coordinates, find distance and bearings) and the direct problem (given a start coordinate, bearing, and distance, find the destination).
Why Flat-Earth Formulas Can Mislead You
If you use simple planar math for points that are far apart, your results can drift noticeably. On a map projection, lines that look straight might not represent the shortest surface path. The shortest path between two points on a sphere is called a great-circle route.
- For short city-scale distances, planar approximations may be acceptable.
- For cross-country or intercontinental distances, geodetic methods are usually essential.
- Bearing also changes along most great-circle routes, so a single constant heading may not remain exact.
What This Calculator Returns
Inverse solution (point A to point B)
- Great-circle distance in km, miles, nautical miles, or meters
- Initial bearing (forward azimuth from start point)
- Final bearing (approach azimuth at destination)
- Midpoint along the great-circle path
Direct solution (start + bearing + distance)
- Destination latitude and longitude
- Coordinates presented in decimal degrees and DMS-style text
Coordinate Input Tips
Enter coordinates in decimal degrees. Use positive values for North and East, and negative values for South and West. A quick reference:
- Latitude range: -90 to +90
- Longitude range: -180 to +180
- Example: New York City is approximately 40.7128, -74.0060
- Example: London is approximately 51.5074, -0.1278
Behind the Scenes: Core Math Concepts
This tool uses the haversine and trigonometric bearing formulas on a sphere with Earth’s mean radius (WGS84 approximation). While high-precision surveying may require a full ellipsoidal model (such as Vincenty or Karney methods), this approach is accurate for many navigation and educational use cases.
In practical terms, you are calculating the central angle between two positions, then converting that angular separation into linear distance using Earth’s radius. Bearings are derived from spherical trigonometry relationships between meridians and the great-circle arc.
Common Use Cases
- Estimating flight route distance between airports
- Planning marine navigation legs
- Calculating delivery service ranges
- Teaching geodesy, GIS, or coordinate systems in the classroom
- Adding coordinate-based features to mapping applications
Accuracy Notes
No geodetic result is meaningful unless the input data is reliable. A GPS reading with weak signal quality can introduce error larger than the mathematical model difference. Always pair computations with sound coordinate collection practices and a consistent datum/reference frame when your project demands precision.