激光雷达探测水体光学特征参数的方法分析

Analysis of Detection Inversion of Water Optical Characteristics by Lidar

多次散射是影响激光雷达探测水体光学特征参数(包括吸收系数a,衰减系数c,漫射衰减系数K_d)的重要因素,而视场(field of view,FOV)是造成接收回波中多次散射比重差异的关键参数.基于Mclean-Walker海洋激光雷达模型,引入接收视场参数θ_(rcvr),分别针对船载、机载和星载平台激光雷达进行探测回波计算,假设探测高度依次为10,300,7×10~5 m,在接收视场变化情况下分析多次散射因子对反演水体光学特征参数的影响。结果表明,利用水体中激光散射回波反演水体光学特征参数的方法中,假定激光准直入射,θ_(rcvr)与探测高度H是影响反演结果的直接因素,激光雷达衰减系数K_lidar的物理意义随之变化,当θ_(rcvr)近似为0时K_(lidar)反演值为衰减系数c,随θ_(rcvr)×H增大,K_(lidar)反演值逐渐接近于K_d。

Multiple scattering is an important factor for measuring water optical characteristic parameters（including absorption coefficient a, attenuation coefficient c, diffuse attenuation coefficient K_d） by lidar. Meanwhile, field of view（FOV） is a key parameter which affects the proportion of multiple scattering in receiving echoes. A parameter of FOV（θ_（rcvr）） is introduced into the inversion method of water optical properties by ocean lidar based on the Mclean-Walker model. In the cases of shipboard, airborne and spaceborne platforms at the height of 10, 300, 7×10~5 m respectively, scattering echoes are calculated according to the lidar theory.The inversion of water optical parameters is analyzed with multiple scattering factor under different FOVs. It is shown that assuming the incident laser of highly collimated,θ_（rcvr） and detecting height H are critical factors which influence inversion results in the method for obtaining water optical parameters from laser scattering echo. It is worth noting that the physical meaning of the lidar attenuation coefficient K_（lidar） changes with the factors.K_（lidar） can be considered as c when θ_（rcvr） is approximately 0. And K_（lidar） gradually approaches K_d with the increase of θ_（rcvr）× H.