(a) (b) (c) (d) (e) (f) Figure 8. The images of the vehicle autonomously navigating (a) and (b) between multiple floors and (c)-(f) in confined indoor environments. A video of the experiments is available at http://mrsl.grasp.upenn.edu/shaojie/ram2012.m4v. (a) (b) (c) (d) Figure 9. The mapping process (a)-(c) across three floors of an indoor environment and (d) a side view of the three-story building. 46 * IEEE ROBOTICS & AUTOMATION MAGAZINE * DECEMBER 2013 Figure 10. The 3-D map of the demonstration site generated during an autonomous flight.http://mrsl.grasp.upenn.edu/shaojie/ram2012.m4v