影响三轴摄影测量试验精度的折射误差分析

    Analysis of refraction error affecting accuracy of triaxial photogrammetry

    • 摘要: 常规三轴试验与数字化测量技术相结合的摄影测量法可实现对土样的局部变形测量,由于折射的影响,其测量精度较低。为减少折射误差,利用摄影测量法对饱和砂土样进行三轴试验。使用相机对土样进行连续环绕拍摄,将获取的相片导入PMS软件中提取坐标,结合光线追踪技术构建三维折射修正模型,经过大量数据分析得到了折射误差修正系数。试验结果表明:在轴向高度上,修正系数为1.006,经修正后相对误差平均值为0.185%;在截面半径上,修正系数为1.361,经修正后相对误差平均值为0.451%,均满足精度要求。本次试验的饱和砂土所获修正系数可减小折射的影响、提高测量精度。

       

      Abstract: The photogrammetry combining conventional triaxial testing with digital measurement technology can measure the local deformation of soil samples.However, the measurement accuracy is relatively low due to the refraction influence.In order to reduce refractive error, the photogrammetry was used to conduct triaxial test on saturated sandy soil samples and some corrective methods were adopted.We took photos of soil samples by continuous surround shooting.The coordinates could be extracted by importing the obtained photos into the PhotoModeler Scanner.A 3D refraction correction model using ray tracing technology was established, and refraction error correction coefficients were obtained by a large amount of data analysis.The test results showed that the correction coefficient at the axial height direction was 1.006 and the average of relative error after correction was 0.185%.The correction coefficient at radius direction was 1.361 and the average of relative error after correction was 0.451%.Both meet the accuracy requirement.For the saturated sandy soil in this test, the correction coefficient can reduce the influence of refraction and improve the measurement accuracy.

       

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