基于地面与低空无人机联合观测场地BRDF建模方法  

Calibration Site BRDF Modeling Method Based on Ground and Low-Altitude UAV Joint Observation

作　　者：何玉青 胡文杰 胡秀清[2,3] 朱吉彪 何兴伟 金伟其 He Yuqing;Hu Wenjie;Hu Xiuqing;Zhu Jibiao;He Xingwei;Jin Weiqi(Key Laboratory of Photoelectronic Imaging Technology and System,Ministry of Education,School of Optics and Photonics,Beijing Institute of Technology,Beijing 100081,China;Key Laboratory of Radiometric Calibration and Validation for Environmental Satellites,National Satellite Meteorological Center(National Center for Space Weather),China Meteorological Administration,Beijing 100081,China;Innovation Center for FengYun Meteorological Satellite(FYSIC),Beijing 100081,China)

机构地区：[1]北京理工大学光电学院光电成像技术与系统教育部重点实验室,北京100081 [2]中国气象局中国遥感卫星辐射测量和定标重点开放实验室,国家卫星气象中心(国家空间天气监测预警中心),北京100081 [3]许健民气象卫星创新中心,北京100081

出　　处：《光学学报》2023年第15期372-384,共13页Acta Optica Sinica

基　　金：国家重点研发计划(2022YFB3902900,2022YFB3902901,2018YFB0504901)。

摘　　要：双向反射分布函数(BRDF)是星载遥感器进行场地替代定标中的重要参量,随着技术的进步,低空自旋翼无人机已经成为了获取场地BRDF的便捷高效手段,通过现场测量准不变定标场的无人机多角度观测光谱数据,建立更加准确的BRDF模型还能进一步挖掘潜力。提出一种基于地-空双光谱仪联合观测加漫射板观测并消除漫射光影响的BRDF建模方法。使用无人机搭载光谱仪进行场地光谱的低空测量,获取半球空间内多角度下的场地光谱数据,同时开展地基光谱仪联合同步测量漫射参考板,连续记录照明光场的变化以及漫射光照明下的场地光谱数据。联合空地双光谱仪对目标和参考板实测的辐亮度数据,结合太阳及观察角度之间的几何观测,计算场地的多角度反射率。基于Ross-Li核驱动半经验模型对多角度反射率数据进行拟合,采用最小二乘法对模型系数进行拟合,以得到最优的场地BRDF模型,并对模型进行漫射光校正。实验证明,经漫射光校正后的BRDF模型各波段的相对偏差均值都在5%以内,相对偏差标准差在3%以内,有效消除了场地BRDF建模在漫射光照射下的干扰,提高了BRDF建模的准确性。Objective The bidirectional reflectance distribution function(BRDF)is a crucial parameter for satellite sensors to conduct vicarious calibration of pseudo-invariant calibration sites(PICS).Low-altitude self-rotating unmanned aerial vehicles(UAVs)have become a convenient and efficient approach for acquiring BRDF data of these sites.When the surface's directional reflection characteristics in outdoor conditions are measured,it is not possible to control the illuminance solely in the non-incident direction.The target is illuminated by direct sunlight and atmospheric scattered light,introducing a certain level of systematic error in BRDF measurement.Conducting in situ measurements through UAVs with multi-angle observation and spectral data shows significant potential for building more accurate BRDF models for PICS.We propose a BRDF modeling method based on joint observations of ground-based and aerial dual spectrometers,and diffuse plate observations to eliminate the influence of diffuse light.The compact and lightweight drone platform,which is not limited by terrain,makes it suitable for measuring various complex terrains.Simultaneously,the ground-based spectrometer can continuously measure changes in the illumination field.The combined observations of the ground-based and low-altitude UAV instruments can eliminate the interference caused by diffuse light irradiation in BRDF modeling and substantially improve accuracy.Methods The synchronized BRDF observation system includes an airborne spectral measurement system,a groundbased spectrometer measurement system,a solar radiometer,and a whole sky imager.The low-altitude UAV carries a spectrometer to obtain site spectral data at multiple angles within a 50 m radius hemisphere.Meanwhile,the ground-based spectrometer is employed to synchronously measure the diffuse reference panel,continuously recording changes in the illumination field and site spectral data under diffuse illumination.The radiative luminance is measured by a ground-based spectrometer,and the BRDF is calc

关 键 词：双向反射分布函数 无人机 双光谱仪 双向反射分布函数建模 漫射光校正 

分 类 号：O436[机械工程—光学工程]