AN INVESTIGATION ON THE ACCURACY OF 3-DIMENSIONAL SPACE RECONSTRUCTION USING THE DIRECT LINEAR TRANSFORMATION TECHNIQUE

An investigation on the three-dimensional calibration errors associate d with the direct linear transformation (DLT) technique was carried ou t using a two video camera system. Thirty different configurations in five groupings of different numbers of control points were tested. The results showed that the accuracy improved as the number of control po ints increased from 8 to 24. Further, it was demonstrated that the bes t accuracy was achieved when the control points were evenly distribute d throughout the control region. For the system under investigation, a n accuracy of 1-2 mm in the x and y directions, 4-6 mm in the z direct ion and 6-7 mm for the resultant was obtained in a control space of 2. 10 x 1.35 x 1.00 m. Additionally, the accuracy for points outside the control space and the systematic error associated with the control obj ect were studied. Tests were done on a 32-point rectangular calibratio n frame, and the results indicated that the calibration errors could b e reduced by 20-40% when an appropriate quadratic function was used to modify the standard DLT method.