4.1.2. Result of tracking
Using the algorithm described above, a sequence of radiographic images is processed for the purpose of weld defect tracking. The position of the weld defect is described in the image coordinate i and j. The coordinates are predicted frame by frame following the procedure described in Section 3.2.2. Predictions of coordinate i and j are illustrated separately by the black solid circles and the blue solid squares in Fig. 5. The observation of the weld defect provides the observed position in the image coordinate i and j, following the image processing procedure described in Section 3.2.3. The observations are illustrated by the black hollow circles and the blue hollow squares in Fig. 5. In the experimental image sequence, the weld defects displace a large range of the image coordinate system. The proposed algorithm is able to track the changing of defect position, despite the variation of velocity.