  Observations of synchrotron polarization at multiple frequencies in the
presence of Faraday rotation can provide a way to reconstruct the 3D magnetic
field distribution. In this paper we compare the well known Faraday Tomography
(FT, Burn 1966) technique to the new approach named Synchrotron Polarization
Gradients (SPG, Lazarian & Yuen 2018b). We compare the strengths and
limitations of the two techniques, and describe their synergy. In particular,
we show that in the situations when FT technique fails, e.g. due to
insufficient frequency coverage, the SPG can still trace the 3D structure of
magnetic field.
