An assessment of the precision and accuracy of methods of digital target location

Abstract This paper presents results of an extension of an earlier investigation on precision of digital target location. An extensive simulation study of the precision of digital target location involving such factors as quality and size of details, image geometry and quantisation level has been carried out to determine accuracies of target location based on least squares template matching techniques and target edges. The results of these tests have been compared with the results obtained in the earlier study based on the centroid determination. Each of the methods indicates that precision of target location can be of the order of 0.02 pixel or better under ideal circumstances. In an example of the application of these methods in a close-range digital photogrammetric study, it is demonstrated that accuracies of target location can be significantly affected by uneven lighting on the subject. The most appropriate method of locating the targets under these conditions was found to be that based on edges of the targets.