基于大口径闪烁法和差分到达角起伏法开展了间距为3.95 km近水平路径的大气相干长度测量实验。测量结果表明：在同路径的上下行光传播方向上，闪烁法测量相干长度的相关系数为0.94，而到达角起伏法测量相干长度的相关系数为0.79。路径权重的理论分析揭示了闪烁法对路径中部的湍涡敏感，且路径权重函数关于路径中部呈对称分布；到达角起伏法对接收端附近的湍涡敏感，其路径权重函数从发射端到接收端呈单调递增趋势。因此，实际的长距离光传输实验中，在不能确定路径中湍流强度分布的情况下，采用闪烁法测量路径上的湍流效应更适宜。

Atmospheric coherence length over a nearly horizontal and 3.95 km path was experimental studied by the large aperture scintillation and differential image motion measure angle-of-arrival fluctuation methods. For two direction (up and down) of the same path, the experiment results show that the correlation coefficient of the large aperture scintillation method is 0.94, while the correlation coefficient of differential image motion measure angle-of-arrival fluctuation method is 0.79. Analysis of path weight function reveals that scintillation is most sensitive to the eddy in the center of the path and its path weight function is symmetrical in the measured path; however, DIMM is most sensitive to the eddy near the receiver and its path weight function is increased monotonically along with measured path from transmitter to receiver. Therefore, the scintillation maybe more appropriate for measuring turbulent effects when light propagate along long distance path whose turbulence intensity distribution is indistinct.