  Multipath and non-line-of-sight (NLOS) signals are the major causes of poor
accuracy of a global navigation satellite system (GNSS) in urban areas. Despite
the wide usage of the GNSS in populated urban areas, it is difficult to suggest
a generalized method because multipath errors are user-specific errors that
cannot be eliminated by the DGNSS or a real-time kinematic technique. This
paper introduces a real-time multipath estimation and mitigation technique,
which considers compensation for the time offset between constellations. It
also presents a mode-switching algorithm between the DGNSS and multipath
mitigating mode and shows that this technique can be effectively utilized for
automobiles in a deep urban environment without any help from sensors other
than GNSS. The availability is improved from 64% to 100% and the error RMS is
reduced from 11.1 m to 1.2 m on Teheran-ro, Seoul, Korea. Because this method
does not require prior information or additional sensor implementation for
high-positioning performance in deep urban areas, it is expected to gain wide
usage in not only the automotive industry but also future intelligent
transportation systems.
