AN ASSESSMENT OF THE PRECISION AND ACCURACY OF METHODS OF DIGITAL TARGET LOCATION

This paper presents results of an extension of an earlier investigatio n on precision of digital target location. An extensive simulation stu dy 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 re sults of these tests have been compared with the results obtained in t he earlier study based on the centroid determination. Each of the meth ods 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 si gnificantly affected by uneven lighting on the subject. The most appro priate method of locating the targets under these conditions was found to be that based on edges of the targets.