Aphid Biology Group, Department of Biology, Imperial College at Silwood Park, Ascot, United Kingdom
We have been using a two-camera, 3-D video system to record the flight behaviour of aphids. The system has two cameras rigidly attached to a base plate, around 20 cm apart and adjusted so that their optical axes converge on a single point, beyond the zone in which the behaviour takes place. The images from the cameras are superimposed so that an insect appears on the monitor screen as two dots, one from each camera. The horizontal separation of the images is linearly related to the distance of the insect away from the camera assembly. Knowing Z, the distance from the camera, it is possible to correct the X and Y coordinates measured from the screen for the effects of perspective and generate an accurate estimate of the position of the insect in space.
All the relationships are linear so the software needed for the conversion is very simple and a video mixer is not necessarily required, just the ability to lock together the synchs of the two cameras. We will present the calibration data for the system and some sample analyses of aphid flight tracks. The analysis software calculates the 3-D speeds, linearity indices, turning rates, directional bias and sinuosities. The horizontal and vertical plane components can also be resolved.