Determination of coordinate prediction errors was made by comparing the reference coordinates with those predicted by the algorithm and also by determination of segment lengths and angles for the triangular object, each of which would be expected to remain constant. The reference markers were used in the algorithm to determine a horizontal position of a given image in the panning rotation. Mean positional errors across 170 images were about 0.84 mm and 0.96 mm in the horizontal and vertical directions, respectively. Segment lengths of the triangular object remained relatively constant across all images of the panning. The three angles of the object also were relatively constant with variability of about 0.4 degrees.
Much kinematic analysis is based on digitizing film or video images of movement patterns.
When such images are quite small fractions of the full recorded image, digitizing error increases substantially because of the difficulty in resolving body landmarks in the small images. Thus, a technique which allows increased image size has potential for reducing the error involved in determining body positions from recorded images. Panning rotation of cameras allows for relatively large image sizes as full field width does not have to be visible. If the panning algorithm itself introduces little systematic error into an analysis, then use of such techniques can help minimize the error associated with digitizing images. The two-dimensional algorithm tested in this study was found to accurately predict position coordinates while introducing only little complication to the calibration, data collection and analysis procedures.