AUTOMATED 3-D TRACKING OF VIDEO-CAPTURED MOVEMENT USING THE EXAMPLE OF AN AQUATIC MOLLUSK

We describe a computer program that tracks the three-dimensional coord inates of a snail (moving within a tank) from images captured by a sin gle video camera. The tank and a mirror placed at 450 to one side are viewed to provide direct and reflected images of a pond snail, Lymnaea stagnalis, moving around the tank. The output of the camera is captur ed with an IBM-compatible PC using a framegrabbing VideoBlaster board. The main features of our Windows program is the frame-by-frame analys is of the captured video, enhancement of contrast, location of dark '' snails,'' discrimination by size, trigonometric determination of the x ,y,z coordinates, and the final export of data in a spreadsheetready f ormat. After the user has outlined the position of the tank on the scr een and set the discrimination thresholds, no further user activity is required. This makes the analysis of slowly moving mollusks much less operator intensive and less tedious. The method is applicable to othe r faster moving organisms (e.g., fish) because the analysis is perform ed on captured video sequences.