  Interplanetary solar radio type III bursts provide the means for remotely
studying and tracking energetic electrons propagating in the interplanetary
medium. Due to the lack of direct radio source imaging, several methods have
been developed to determine the source positions from space-based observations.
Moreover, none of the methods consider the propagation effects of anisotropic
radio-wave scattering, which would strongly distort the trajectory of radio
waves, delay their arrival times, and affect their apparent characteristics. We
investigate the source positions and directivity of an interplanetary type III
burst simultaneously observed by Parker Solar Probe, Solar Orbiter, STEREO, and
Wind and compare the results of applying the intensity fit and timing methods
with ray-tracing simulations of radio-wave propagation with anisotropic density
fluctuations. The simulation calculates the trajectories of the rays, their
time profiles at different viewing sites, and the apparent characteristics for
various density fluctuation parameters. The results indicate that the observed
source positions are displaced away from the locations where emission is
produced, and their deduced radial distances are larger than expected from
density models. This suggests that the apparent position is affected by
anisotropic radio-wave scattering, which leads to an apparent position at a
larger heliocentric distance from the Sun. The methods to determine the source
positions may underestimate the apparent positions if they do not consider the
path of radio-wave propagation and incomplete scattering at a viewing site
close to the intrinsic source position.
