Schematic illustration of the analysis method to estimate the LOS magnetic field strength. The Zeeman shift is either negligible compared to the spectral line width (left) or on the same order of magnitude (right). In the lower left image, the ratio of dI/ dν to V is proportional to the magnetic field strength in LOS direction Bcosθ. The estimation of the LOS magnetic field strength from the spectral line in the lower right image varies significantly from the present LOS magnetic field strength in the model.