  This paper proposes a new and efficient method to estimate 6-DoF ego-states:
attitudes and positions in real time. The proposed method extract information
of ego-states by observing a feature called "TROVE" (Three Rays and One
VErtex). TROVE features are projected from structures that are ubiquitous on
man-made constructions and objects. The proposed method does not search for
conventional corner-type features nor use Perspective-n-Point (PnP) methods,
and it achieves a real-time estimation of attitudes and positions up to 60 Hz.
The accuracy of attitude estimates can reach 0.3 degrees and that of position
estimates can reach 2 cm in an indoor environment. The result shows a promising
approach for unmanned robots to localize in an environment that is rich in
man-made structures.
