EVALUATION OF PLANAR RECONSTRUCTION ACCURACY FOR TWO TECHNIQUES INCORPORATING CAMERA TILT

Mark Brewin¹, David Kerwin¹ and Paul McCombie².

¹Department of Sport & Exercise Science, University of Bath, Bath, UK. ²Department of Architecture & Civil Engineering, University of Bath, Bath, UK.

Planar analyses of sporting activities routinely employ scaling techniques with the camera elevated above the activity. An alternative technique for planar reconstruction can be derived from the DLT. This study compared reconstruction accuracy for scaling with 2D-DLT for a large field of view as camera tilt increased. Four calibration and 30 reconstruction markers on a vertical plane were recorded at tilt angles from 0° to 6°. Locations for the reconstruction markers were estimated using both techniques and compared to their known values. The smallest reconstruction errors were obtained using 2D-DLT and were unaffected by tilt angle (P<0.01). An increased tilt angle produced significantly larger errors (P<0.01) for scaling than 2D-DLT. 2D-DLT provided accurate reconstruction data over a range of tilt angles and should be adopted for planar analyses of sporting activities.