Looking at the documentation for the Factored Quaternion Algorithm (FQA). In section 2 they define NED as the traditional Earth's fixed coordinate system, thereby referring to 'true' north. However, it is unclear to me how this is accounted for within the actual algorithm.

In section 2. D) it is stated:

In the absence of measurement error, e_m should agree with the known local normalized magnetic field vector n = [nx ny nz]

I infer from this (perhaps incorrectly) that the normalized local magnetic field vector is relative to magnetic north.

Looking up the definition for the WMM components yields a relationship between the x and y horizontal components and the declination, but is anyone able to verify that the WMM x, y, z components are relative to true north? And thus, that the FQA accounts for declination?



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