@INPROCEEDINGS{fu2019icra,
  author={Fu, Bo and Shankar, Kumar Shaurya and Michael, Nathan},
  booktitle={2019 International Conference on Robotics and Automation (ICRA)},
  title={RaD-VIO: Rangefinder-aided Downward Visual-Inertial Odometry},
  year={2019},
  volume={},
  number={},
  pages={1841-1847},
  doi={10.1109/ICRA.2019.8793741}}