Accuracy assessment and control point configuration when using the DLT for photogrammetry.

The direct linear transformation (DLT) is a common technique used to calibrate cameras and subsequently reconstruct points filmed with two or more cameras in a three-dimensional object space. The assessment of the accuracy of this technique, and of the influence of the distribution of control points on accuracy were examined. It was concluded that to obtain a true estimation of reconstruction accuracy, an independent assessment criterion is required, and that the use of control points distributed around the outside, rather than within the space to be calibrated, is preferred.