  Direct solar coronal magnetic field measurements have become possible since
recent development of high-sensitivity infrared detection technology. The
SOLARC instrument installed on Mt. Haleakala is such a polarimetric coronagraph
that was designed for routinely observing Stokes parameter profiles in near
infrared (NIR) wavelengthes. The Fe$^{+12}$ 1075 nm forbidden coronal emission
line (CEL) is potential for weak coronal magnetic field detection. As a first
step the potential field model has been used to compare with the SOLARC
observation in the Fe$^{+12}$ 1075 nm line (Liu and Lin 2008). It's found that
the potential fields can be a zeroth-order proxy for approaching the observed
coronal field above a simple stable sunspot. In this paper we further discuss
several nodi that are hampering the progress for reconstructing the real
coronal magnetic field structures. They include the well-known Van Vleck effect
in linear polarization signals, ignorance of the information of the NIR
emission sources (i.e., inversion problem of coronal magnetic fields), a fat
lot of global non-linear force-free field tools available for better modeling
coronal magnetic fields, and so on.
