Use this cartographic calculation to convert, scale, or compare map, terrain, bearing, raster, or route quantities when the coordinate and unit conventions are explicitly known.

Forward Azimuth Degrees (deg)

Required number input.

Reverse azimuth, normalized to [0,360), from a forward azimuth in degrees. The tool evaluates the supplied inputs together and returns the named outputs below; it does not infer omitted operating conditions or change the units shown.^[1]

Back Azimuth Degrees (deg)

The resulting back azimuth degrees returned as a number.

• Map calculations depend on datum, projection, latitude, scale definition, magnetic-declination epoch, and whether distances are planar, rhumb-line, or geodesic. A compact formula cannot remove distortion or infer the missing reference system.
• Use finite inputs in the displayed units and preserve more precision than the final presentation requires. Independently verify safety-critical, financial, compliance, or production decisions.

Confirm the map datum, projection, scale, and bearing convention before applying the result. Use geodesic or GIS software with current reference data when survey-grade or navigation-critical accuracy is required.

• Great Circle Initial Bearing

  Initial spherical great-circle bearing from the first latitude/longitude to the second, normalized to [0,360).

• Interior Angle Two Bearings

  Smallest unsigned angle between two azimuth bearings in degrees.

• Declination Drift Adjuster

  Project signed east-positive magnetic declination using a signed annual change in degrees per year.