针对科研与工程中转角测量优于5″的高精度要求,提出了一种用直线做特征标志的基于图像的测量方法。用高分辨率相机采集被测物上长直线标志,通过高精度检测图像上直线的倾斜角度来计算转角。分析了基于图像高精度角度测量中出现的多种原来无需考虑的影响精度的因素。给出了角秒级角度测量时直线的拟合检测算法以及直线标志的成像宽度、长度、与采样方向的角度等参量的选择应满足的条件。仿真和实验结果表明直线宽度5～9 pixel,直线方向避开与采样方向成0°和45°角时角度检测精度达到最优,当直线长度不小于1000 pixel时测量精度优于5″。

A measurement method based on image is present to measure rotation angle at high precision of 5″ which uses a line as the character sign. A digital camera is used to capture the image of the line. The rotation angle is calculated by detecting the line slope angle with high accuracy in the image. The factors that affect the precision are analyzed. Then the guidelines to measure a rotation angle with high precision of seconds are proposed, which include the method to detect a line and the parameters of a line such as the length,the width and the direction. Experiments show that when the line is wide of 5～9 pixel and the angle between the line and the sampling direction is far away from 0° and 45° the rotation angle measurement gets the highest accuracy, and if the length is not less than 1000 pixel the precision is not less than 5″.