RUIZ-VEGA, JOSE A.* ; STEVENSON, R.D.; Univ. OF Massachusetts Boston: A two-camera video system to measure animal locomotion outdoors

Most research done on animal locomotion has been restricted to controlled laboratory settings, where animals move at constant velocity, or perform a standardize burst acceleration or jump. Few data exist for animals in the own environments because scientists lack good methods to quantify motion in the field. In response to this need, our lab is designing a field-portable, two-camera video system that can be used to reconstruct the trajectory of moving objects in three dimensions. Each camera is moved by an operator. The pan and tilt angles of each camera are measured with a subsystem of optical shaft encoders manufactured by Peak Performance, Inc. These angle data are recorded along with the time on the video image. With this information and data on the camera locations, it is possible to triangulate the position of an object in three-dimensional space. After obtaining the position data, we then analyze the video using advanced image processing software, Visual Fusion�. This software has the ability to track multiple objects from frame to frame, reducing the time it takes to analyze data. Errors in the measurement system result from accuracy of the sensor location, sensor to target line of sight knowledge (including sensor bore sight, optical system, target pixel location in image) and the geometry of the measurement system. Each of these errors is estimated and their contributions to position error are calculated using the error propagation equations given by Sanders-Reed, J. 2001. Optical Engineering. 40:627-636.