两种BRDF室外测量方法的RGM模拟对比与误差分析

目标物的反射特性,无论是在遥感模型还是在遥感反演中都扮演着重要的角色,因此选用正确的自然条件下目标物反射特性的测量方法是遥感定量分析的基础.长期以来在自然条件下(即太阳直射光和天空漫射光同时存在)测量目标物的反射特性时,可以获得BRF(Bidirectional Reflectance Factor)作为目标反射特性的描述,但这样获得的BRF与辐射环境有关.为了消除辐射环境的影响,获得真正能够反映目标物的反射特性的BRDF(Bidirectional Reflectance.Distribution Function),前人提出了一些野外测量的方法.本文在此基础上,利用计算机模拟的辐射度(Radiosity)模型在真实场景基础上模拟BRF值,分析测量方法中存在的系统误差受观测条件影响的大小,比较了测量方法的优劣,提出了野外测量时选择测量方法的基本原则.

Two Methods of Acquiring BRDF of Object in the Field Simulated with Radiosity-graphics Combined Model and Error Analysis

The bidirectional reflective characteristic of objects plays an mi portant role not only in models of remote sensing but also in inversion. Consequently, it is the basis ofquantitative analysis in remote sensingwith the appropriate method of acquiring the bidirectional reflective characteristic of objects in natural environment. For a long period, BRF (BidirectionalReflectance Factor) acquired in natural environmentand related to radiantenvironment, is regarded as the expression ofbidirectional reflective characteristic ofobjects. There are differenceswhichmustbe considered betweenBRF and real value except in a strict clear day. In order to elmi inate the influence of the environment radiance, somemethod acquiring BRDF (Bidirectional Reflectance Distribution Function) data of objects in natural environment have been designed. But the erroroccurred in thesemethod hasnotbeen strictly analyzed. In thispaper thesemethods are compared by using radiosity-graphic combined model based on three dmi ensional structures which is one of computer smi ulation mode.l And their fixed error affected by conditions acquiring BRDF data is analyzed in the smi ulation. We also provide principles to choose the suitablemethod of acquiringBRDF data in natural environment. By these principleswe can take the most suitable method under different conditions in order to reduce the error and get acceptable value from measurement.