Distance and velocity estimation using optical flow from a monocular camera

Hann Woei Ho*, Guido C.H.E. de Croon, Qiping Chu

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

24 Citations (Scopus)
42 Downloads (Pure)


Monocular vision is increasingly used in micro air vehicles for navigation. In particular, optical flow, inspired by flying insects, is used to perceive vehicle movement with respect to the surroundings or sense changes in the environment. However, optical flow does not directly provide us the distance to an object or velocity, but the ratio of them. Thus, using optical flow in control involves nonlinearity problems which add complexity to the controller. To deal with that, we propose an algorithm that estimates distance and velocity of the vehicle based on optical flow measured from a monocular camera and the knowledge of control inputs. This algorithm applies an extended Kalman filter to state estimation and uses the estimates for landing control. We implement and test our algorithm in computer simulation and on board a Parrot AR.Drone 2.0 to demonstrate its feasibility for micro air vehicles landings. Results of the simulation and multiple flight tests show that the algorithm is able to estimate height and velocity of the micro air vehicles accurately, and achieves smooth landings with these estimates, even in windy outdoor environments.

Original languageEnglish
Pages (from-to)198-208
Number of pages11
JournalInternational Journal of Micro Air Vehicles
Issue number3
Publication statusPublished - 1 Sep 2017


  • autonomous landing
  • Distance estimation
  • efference copy
  • monocular vision
  • optical flow


Dive into the research topics of 'Distance and velocity estimation using optical flow from a monocular camera'. Together they form a unique fingerprint.

Cite this