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These equations can be used to solve for sin A and cos A and thus an unambiguous best fit azimuth can be derived from the observations. The unit vectors can be calculated and the theoretical readings subtracted from the observed readings to produce residuals for each observation and each axis. ons nsc l f c o ndb sfo chs nso un l h sumof h sdu ls squared is minimized. In the following graphs for all 6 corrections, a clear minimum sum squared occurs at the best value for each correction: A ‘Mon lo’ n lyss s h n unfo
Figure 67: Correcting magnetic station observations.
All previous raw surveys up to that point are then corrected with this latest estimate and the azimuths recalculated as if there was no magnetic interference present.
In practice the data will be noisy and often requires some filtering before it can be used. Any bad readings are either weighted low in the least squares calculation or they are removed altogether.
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