Bees’ guidance strategy for avoiding crash landings
Landing safely is a difficult aspect of flight, because the rate of approach must be reduced to near zero at touchdown.
This is hard enough on horizontal surfaces, but even more challenging as inclination increases, i.e. when landing on surfaces of different orientation. Yet honey bees achieve this easily, hundreds of times per day.
To the amazement of engineers who had unsuccessfully tried lasers, radars, sonars and GPS technology in striving to design autonomous landing systems for flying robots, the bees’ guidance strategy is “surprisingly simple”.1,2 Experiments show that bees land safely by simply ensuring that the surface they are approaching expands at a constant rate within their field of vision.1 This is a form of optic flow monitoring,3 which we have noted before.4
Mandyam Srinivasan, professor of visual neuroscience at the University of Queensland, Australia, explained:
“If you come in [to land] at a constant speed, the image [of the landing strip] appears to expand faster as you get closer. But if you keep the rate of expansion of the image constant, you automatically slow down and by the time you make contact you’re moving at almost zero speed.”2
Mathematical modelling showed that the bees’ simple visual ‘autopilot’ technique worked on almost any type of surface—including walls and flowers—and did not need any information about airspeed or distance from destination.
“Why didn’t we think of this before?” lamented Professor Srinivasan.2 He said that robotic aircraft could soon be equipped to mimic the bee’s landing strategy using a simple, lightweight video camera. The image-only landing technique could also be applied to stealth military planes (no radar or sonar for an enemy to detect) and spacecraft (landing on other planets without GPS to guide them). However, it’s most doubtful that the computer required for this programming would be as tiny as a bee’s brain!
It’s surely self-evident that no ‘guidance strategy’ came about by itself.5 And the One who designed that of the bee has also given us the ultimate ‘guidance strategy’ to avoid the ultimate ‘crash landing’ (Colossians 1:16–20, Romans 10:9, Revelation 20:15).
References and notes
- Baird, E., Boeddeker, N., Ibbotson, M., and Srinivasan, M., A universal strategy for visually guided landing, Proceedings of the National Academy of Sciences (USA) 110(46):18686–18691, 2013.
- Ross, J., Bees no drones when it comes to landing, theaustralian.com, 29 October 2013.
- Esch, H., Zhang, S., Srinivasan, M.V. and Tautz, J., Honeybee dances communicate distances measured by optic flow, Nature 411(6837):581–583, 31 May 2001.
- Sarfati, J., Can it bee? Creation 25(2):44–45, 2003; creation.com/bee.
- For many other examples of human engineers wanting to copy the Master Engineer’s designs in nature, see creation.com/biomimetics. Return to text.
I had been using the technique for docking in Orbiter Spaceflight Simulator and Kerbal Space Program for years prior to the article's publication: observing how many pixels on my computer monitor the station (or part thereon) was gobbling up and reducing my speed so as to keep the rate constant. It was so intuitive that I didn't think it needed explaining.
The correspondent’s submission was received after the two-week period for receiving comments had closed. In this very rare case we are making an exception to our normal rules and have decided to publish the comment because it highlights and adds to the significance of the material presented in the original article. Many thanks to Terry W for taking the time to contribute this.
Whilst I find it fascinating that bees use this technique, I am a little surprised that the experience of pilots for nearly a century had not been taken into account. On a visual approach to landing, pilots use the relative size of the runaway to judge their approach rather than focus on the altimeter. When you have very limited cues regarding height and distance, the change in size of the landing zone serves very nicely, once you have some experience with the technique. That is a far cry from the requirements of an autonomous landing system on a variety of surfaces, but the basic idea might have been useful as a starting point.
Dear CMI -
Man has been making autonomous landing craft for quite a long time. One is on Venus, several are on the moon and on Mars, and many are on earth - one just made the news about a week ago. This is not as insurmountable a problem as you imply.
Our article does not say, nor imply, that the challenge of building craft capable of landing autonomously as bees do was an insurmountable problem. Nor did it say that man has not been able to previously make autonomous landing craft.
Rather, the thrust of the article is summed up in Professor Srinivasan's apt 'soundbite': "Why didn't we think of this before?"
And perhaps I should take this opportunity to expand more overtly the rather 'softly, softly' ending to the article. While bees and all other creatures were created by God along with humans, there is one huge difference worth noting in context of man's engineering capabilities. We were created in the image of the Creator Himself (Genesis 1:26–27), so no wonder man alone among all the creatures has the creative talent and capacity to think and make things, and to study and even copy what God has made. And if ever our creations match some aspect of His handiwork, we should never forget Who thought of it first.