一种仅需距离控制的模型试验平面位移场单像视觉测量

2D DISPLACEMENT FIELD MEASUREMENT FOR MODEL EXPERIMENT BY SINGLE-VIEW METROLOGY WITH RANGE CONTROLS

以高速公路滑坡与路堑边坡物理模型试验的平面位移场测量为例,采用一种无需模型坐标控制的视觉测量方法代替常规的物理或机械方法测量平面位移场。以普通数码相机为测量工具,不需要基准点的坐标而只需测量部分基准点间的距离即可恢复模型平面与像平面间的单应关系,使得测量工作不依赖大地测量仪器。试验过程中相机的内、外方位元素固定,且近似垂直于模型平面,经标志点影像坐标量测,单应矩阵检验后得到模型坐标,消除刚体位移后得到模型的平面位移场。解算结果表明,解析处理结果高于立体解算的精度,可用于亚毫米级精度的平面位移测量。

A single-view vision metrology with range controls is used in displacement measurement of highway landslide and cutting slope model experiment instead of commonly used physical or mechanical methods. It applies non-metric digital camera as the main tool, and only needs some distances of data points instead of coordinate controls on model plane. The homography between model plane and image plane can be recovered by the constrained least-square adjustment, which avoids the dependence on particular geodetic instruments such as theodolites or electronic total stations. The camera is placed perpendicularly to the object plane, and interior and exterior parameters are fixed during experimental period to capture one ortho-image of the model plane at each epoch. Then, the displacement field can be acquired through the post processing of the captured image sequences by the procedures of target accurate measurement, homography matrix calibration, the lens distortions and rigid body transformation displacement elimination. The results indicate that the approach is more convenient and with higher precision, which can be used in engineering applications with accuracy requirement less than 1 mm.