Deformation Measurement of a Railroad Bridge Using a Photogrammetric Board without Control Point Survey

Figure 8

Circle targets and feature points on the photogrammetric board, which were automatically obtained using 10 different feature extraction methods; the 36 points of the photogrammetric board and the extracted feature points (a) and the enlarged view of the detected features in one circle (b). The blue “X” represents the extracted feature points, and the red “+” shows the center of the inner white circle in (b). In (a), the number of extracted feature points in blue is too large in FAST, BRISK, and the like, so some target points do not appear well.

(a)

(b)