Abstract: In response to the problem of large deviation between measured values and calibrated values,as well as inaccurate proportion scaling of industrial photogrammetric scale-bar in actual engineering,a benchmark length error model was derived using retroreflective targets(RRT) as the research object.Experimental research was conducted on RRT roundness,centering robustness,consistency of scale-bar length calibration,and standard length testing.The results showed that the roundness and centering robustness of the die-cutting coated RRT were much higher than other types of RRT.The repeatability of length calibration of the die-cutting coated RRT scale-bar was 1μm,which was better than the repeatability of length calibration of the printed RRT scale-bar.The measurement error of the standard length using the die-cutting coated RRT scale-bar was about 33% smaller than that of the printed RRT scale-bar.Therefore,selecting die-cutting coated RRT as the benchmark target for the scale-bar has important reference significance for improving the measurement accuracy of industrial photogrammetric systems.

Key words: Retro-reflective target；Industrial photogrammetry, Scale-bar, Calibration