利用多角度影像计算BRDF的方法与系统实现

Method and Realization of Calculating BRDF System with Multi-angle Images

BRDF(二项分布函数)可以描述地表的方向反射特性,是定量遥感中多角度遥感研究的前沿热点问题之一。为了研究在不同观测角度下地物的反射情况,主要采用航空摄影测量的方法,利用低空无人机多角度影像获取计算BRDF所需的数据,以共线方程和半经验核驱动模型理论为基础,采用C#面向对象编程(OOP)的实现方法,基于SFM算法求解相机参数以及建立影像金字塔的方式读取影像数据实现了利用多角度影像计算BRDF系统的开发。利用旋翼无人机搭载Micro-MCA六通道多光谱相机获得多光谱影像数据,以土壤和玉米地面点为试验对象,将系统得到的极化图结果与BRDF模拟软件(DART)的影像进行分析和比较。结果表明:该系统计算结果高效精准,且具有良好的鲁棒性,通过核驱动模型的外推得到的任意角度二向反射率符合BRDF的特点,"热点"出现在观测角与太阳同侧,与DART模拟影像的反射率变化趋势吻合;系统中设计的多尺度模块,能够满足影像不同空间分辨率下的计算要求。系统的实现为定量遥感中多角度研究BRDF的后续研究提供了参考依据。

BRDF（Binomial Distribution Function）can describe the reflection characteristics of the surface,one of the cutting-edge hot issues in multi-angle research in quantitative remote sensing.In order to study the reflection of the objects at different angles of observation,the measurement data are obtained by using the aerial photogrammetry method.Based on the collinear equation and semi-empirical core-driven model theory,the measurement of BRDF system with Multi-angle Image is realized by using C# object-oriented programming,including SFM（Struct From Motion）algorithm to solve camera parameters and establishment of the image pyramid to read image data efficiently and accurately.The system polarized graph were generated by selecting soil and maize ground point in the multispectral image data obtained by using the Micro-MCA six-channel multi-spectral camera,compared and analyzed with the image of the BRDF simulation software（DART）.The results show that the system is computationally efficient and robust.The reflectivity of any observation angle extrapolated from the core driving model is in accordance with the characteristics of BRDF.The＂hot spot＂appears at the same side observation of the sun,which is consistent with the change trend of reflectivity of DART simulation image.The multi-scale module designed in the system can meet the calculation requirements under different spatial resolution of image.The realization of the system provides a reference for the follow-up study of multi-angle measurement of BRDF in quantitative remote sensing.