This should be a basic geodesy question.

I have a requirement to calculate "bearing (magnetic)" between two points. Will the igismap Bearing Angle tool do the job or is there something more to consider give that there is a requirement for a "magnetic" bearing.

I am hoping for a web based solution.

  • If you don't find a web based solution then please use a new question to seek an ArcGIS Desktop one or if this gets no answers you could edit "web based" out and ArcGIS Desktop in.
    – PolyGeo
    Nov 14, 2019 at 0:22

1 Answer 1


Yes, there is something more to consider: the Magnetic Declination.

This is a scalar variable, derived from a physical property: the Earth's magnetic field.
It is variable dependant to location and time.


Magnetic Bearing will be the True Bearing plus the Magnetic Declination, for that point and that date.

MB = TB + MD

There are some web resources in the External links section of the Magnetic declination Wikipedia page.

I leave here the link to the Declination calculator of the National Geophysical Data Center.

  • Out of interest, why does the title reference US/UK when it's the entire planet shown? Dec 3, 2019 at 3:59
  • 1
    The Model is for the World. US/UK are the producers of the information. Dec 3, 2019 at 4:37

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