  The line-of-sight (LOS) component of the large-scale photospheric magnetic
field has been observed since the 1950s, but the daily full-disk observations
of the full vector magnetic field started only in 2010 using the SOLIS Vector
Stokes Magnetograph (VSM) and the SDO helioseismic and magnetic imager (HMI).
Traditionally, potential field extrapolations are based on the assumption that
the magnetic field in the photosphere is approximately radial. The validity of
this assumption has not been tested yet. We investigate here the structure and
evolution of the three components of the solar large-scale magnetic field in
2010 - 2017, covering the ascending to mid-declining phase of solar cycle 24,
using SOLIS/VSM vector synoptic maps of the photospheric magnetic field. We
compare the observed VSM vector magnetic field to the potential vector field
derived using the VSM LOS magnetic field observations as an input. The new
vector field data allow us to derive the meridional inclination and the azimuth
angle of the magnetic field and to investigate their solar cycle evolution and
latitudinal profile of these quantities. SOLIS/VSM vector data show that the
photospheric magnetic field is in general fairly non-radial. In the meridional
plane the field is inclined toward the equator, reflecting the dipolar
structure of the solar magnetic field. Rotationally averaged meridional
inclination does not have significant solar cycle variation. While the vector
radial component $B_r$ and the potential radial component $B_r^{PFSS}$ are
fairly similar, the meridional and zonal components do not agree very well. We
find that SOLIS/VSM vector observations are noisy at high latitudes and suffer
from the vantage point effect more than LOS observations. This is due to
different noise properties in the LOS and transverse components of the magnetic
field, which needs to be addressed in future studies.
