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[IEEE 2018 IEEE 3rd International Conference on Image, Vision and Computing (ICIVC) - Chongqing (2018.6.27-2018.6.29)] 2018 IEEE 3rd International Conference on Image, Vision and Computing (ICIVC) - High Accuracy Smartphone Video Calibration for Human Foot Surface Mapping
摘要： Although the digital camera is readily available and the price is decreasing, many users still consider it an expensive device that can be dispensed with by using a smartphone camera. However, both the digital camera and the smartphone need to be calibrated to extract three dimensional (3D) space information from (2D) and to obtain accurate results. This study used close range photogrammetry to calibrate two high resolution digital cameras and a Samsung Galaxy smartphone to find whether any one of them give high accuracy 3D coordinates of the retro-reflective targets that were determined using the self-calibration bundle adjustment method in two phases. The first phase is during walking when 3 trials are conducted. The same three cameras are used for each trial. The second phase is during standing when one trial is conducted. Each of the camera types is placed in front of the platform. The results showed that arguably, the Samsung Galaxy S6 camera is most significant than other cameras in term of accuracy. In addition, this study provides information on how to calibrate one board from other board that has already been calibrated.
关键词： bundle adjustment,calibration,smartphone,scale bar,human foot
更新于2025-09-23 15:23:52
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Methods to calibrate a three-sphere scale bar for laser scanner performance evaluation per the ASTM E3125-17
摘要： A scale bar with sphere targets is one way of realizing the symmetric and asymmetric length tests to evaluate Terrestrial Laser Scanner (TLS) performance per the ASTM E3125-17 standard. The length of the scale bar is required to be known with an expanded (k = 2) uncertainty that must be at least four times smaller than the manufacturer’s maximum permissible error (MPE) specification of the instrument being tested. In this paper, we propose two methods to calibrate the scale bar length using a laser tracker. The first method, which we refer to as the four-orientation and two-face (FOTF) method, is proposed for calibrating the scale bar when it is in a horizontal orientation. The other method, which we refer to as the comparison method, is proposed for calibrating the length of the scale bar in any orientation. We describe the methods, present underlying theories, discuss validation experiments, and summarize results. The two calibration methods are beneficial for the realization of the ASTM E3125-17 standard for TLS performance evaluation.
关键词： Three sphere scale bar,ASTM E3125-17,Terrestrial laser scanner,Laser tracker,Length calibration
更新于2025-09-16 10:30:52
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Simultaneous All-Parameters Calibration and Assessment of a Stereo Camera Pair Using a Scale Bar
摘要： Highly accurate and easy-to-operate calibration (to determine the interior and distortion parameters) and orientation (to determine the exterior parameters) methods for cameras in large volume is a very important topic for expanding the application scope of 3D vision and photogrammetry techniques. This paper proposes a method for simultaneously calibrating, orienting and assessing multi-camera 3D measurement systems in large measurement volume scenarios. The primary idea is building 3D point and length arrays by moving a scale bar in the measurement volume and then conducting a self-calibrating bundle adjustment that involves all the image points and lengths of both cameras. Relative exterior parameters between the camera pair are estimated by the five point relative orientation method. The interior, distortion parameters of each camera and the relative exterior parameters are optimized through bundle adjustment of the network geometry that is strengthened through applying the distance constraints. This method provides both internal precision and external accuracy assessment of the calibration performance. Simulations and real data experiments are designed and conducted to validate the effectivity of the method and analyze its performance under different network geometries. The RMSE of length measurement is less than 0.25 mm and the relative precision is higher than 1/25,000 for a two camera system calibrated by the proposed method in a volume of 12 m × 8 m × 4 m. Compared with the state-of-the-art point array self-calibrating bundle adjustment method, the proposed method is easier to operate and can significantly reduce systematic errors caused by wrong scaling.
关键词： scale bar,relative orientation,self-calibration,stereo photogrammetry,3D vision
更新于2025-09-04 15:30:14