@article{engel14ras,
  author = {J. Engel and J. Sturm and D. Cremers},
  title = {Scale-Aware Navigation of a Low-Cost Quadrocopter with a Monocular Camera},
  journal = {Robotics and Autonomous Systems (RAS)},
  year = {2014},
  volume = "62",
  number = "11",
  pages = "1646-–1656"
}