Calculate the initial great-circle azimuth from Point A to Point B using latitude and longitude. The result is measured clockwise from true north on a spherical Earth model.
This calculator returns the initial azimuth at Point A. Azimuth increases clockwise from true north: 0° is north, 90° east, 180° south, and 270° west.
The 16-point compass label is a convenience classification. Each label spans a 22.5° sector; the degree value is the actual calculated output.
With Point A latitude φ₁, Point B latitude φ₂, and longitude difference Δλ, the calculator evaluates:
This is a spherical model. It is useful for general geographic direction and great-circle reasoning, but it is not an ellipsoidal surveying solution. High-precision geodesy normally solves the inverse geodesic problem on a reference ellipsoid such as WGS84.
This is the direction at departure under the calculator's spherical model. A WGS84 ellipsoidal inverse solution is slightly different, so the two values should not be mixed as though they came from the same model.
On most great-circle routes, the direction changes as you move along the path. The initial azimuth from A to B therefore is generally not just 180° away from the initial azimuth from B to A.
Use Swap A ↔ B when you need the initial direction for the reverse trip. Do not infer it by simply adding or subtracting 180° unless the geometry of the route makes that valid.
If A and B represent the same point, there is no direction from A to B. The calculator returns no azimuth instead of manufacturing a 0° result.
Exact opposite points on a sphere can be connected by infinitely many great circles, so there is no unique initial great-circle azimuth. The calculator reports that case explicitly.
Latitude and longitude define the result relative to geographic north. A magnetic-compass course requires a location- and date-specific magnetic declination adjustment that this calculator does not perform.
For boundary, engineering, or other precision work, use an ellipsoidal geodesic method and the coordinate reference system required by the project. This spherical result should not be presented as a survey-grade bearing.
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