本文選題：輻射度模型 + 二向反射因子�。� 參考：《吉林大學(xué)》2017年碩士論文

【摘要】：早期遙感應(yīng)用中,在研究地表反射率時,人們通常假設(shè)地表為朗伯體,地表在各個方向為朗伯反射,與入射輻射方向、觀測方向無關(guān)。雖然這種假設(shè)在建模計算過程中簡單方便,但大量實(shí)踐證明,自然界中的地表均存在不同程度的非朗伯特性,即二向性反射特性,尤其是在植被反射中二向性反射特性更加明顯。隨著遙感技術(shù)的發(fā)展,尤其是多角度遙感衛(wèi)星的應(yīng)用及二向反射特性理論研究的深入,人們在植被二向性反射特性研究取得的成果也日益成熟,比如輻射傳輸模型、幾何光學(xué)模型、混合模型和計算機(jī)模擬模型等,并得到了國內(nèi)外的廣泛認(rèn)可。在植被遙感領(lǐng)域中,植被二向性反射特性一直是植被多角度遙感研究的理論基礎(chǔ)。由于植被本身結(jié)構(gòu)的復(fù)雜性、實(shí)驗觀測儀器與衛(wèi)星數(shù)據(jù)的局限性以及模型的自適性使得植被二向性反射特性研究難以達(dá)到理想精度。尤其對于較大形體的樹木而言,根據(jù)樹木真實(shí)生長結(jié)構(gòu)盡可能減少抽象簡化從而精確計算其冠層二向反射因子(BRF)相對更加困難。鑒于此本文采用輻射度模型基于樹木真實(shí)結(jié)構(gòu)場景的三維模擬基礎(chǔ)上完成冠層二向反射特性的模擬與分析。輻射度模型主要包括兩部分:一是基于L-系統(tǒng)模擬三維真實(shí)場景,二是在此基礎(chǔ)上采用輻射度方法完成冠層BRF模擬。本文研究內(nèi)容如下:選取植被冠層輻射度模型RGM為研究工具,模擬太陽主平面與垂直主平面方向上的二向反射率因子。輸入?yún)?shù)包括三維結(jié)構(gòu)文件、光譜文件、太陽和天空定義文件、土壤文件、溫度場文件等,計算出可見光及近紅外四個波段的樹木冠層BRF值。為研究模型參數(shù)變化對冠層BRF影響,分別模擬了不同組分、葉子結(jié)構(gòu)、太陽位置、場景參數(shù)(如視場角、天空光比例、下墊面類型)條件下各個波段的冠層BRF,并分析相應(yīng)的變化規(guī)律。結(jié)果表明不同的模型參數(shù)變化時,冠層BRF會呈現(xiàn)不同的變化規(guī)律,如葉面積指數(shù)增大,相應(yīng)的BRF值降低;太陽天頂角的變化會導(dǎo)致冠層BRF熱點(diǎn)移動;視場角越大,熱點(diǎn)效應(yīng)越弱;天空漫射光比例越大,冠層BRF越低;下墊面類型的不同會導(dǎo)致冠層BRF發(fā)生相應(yīng)的變化。本文基于以上結(jié)論,結(jié)合野外實(shí)測樹木結(jié)構(gòu)參數(shù)采用擴(kuò)展L-系統(tǒng)完成樹木三維場景模擬,繼而計算整個場景冠層BRF,并與實(shí)測冠層BRF數(shù)據(jù)進(jìn)行驗證。結(jié)果表明,冠層BRF模擬值與實(shí)測值平均相關(guān)系數(shù)均在0.7以上,說明基于RGM模型冠層BRF模擬計算較為準(zhǔn)確,同時驗證了本次研究實(shí)驗的可靠性。
[Abstract]:In the early application of remote sensing, when studying the surface reflectivity, people usually assume that the surface is Lambert body, and the surface is Lambert reflection in all directions, which has nothing to do with the direction of incident radiation and the direction of observation. Although this assumption is simple and convenient in modeling and computing, a large number of practices have proved that the surface of the earth in nature has varying degrees of non-Lambert characteristics, that is, bidirectional reflectivity. Especially in vegetation reflection, bidirectional reflection is more obvious. With the development of remote sensing technology, especially the application of multi-angle remote sensing satellite and the theoretical research of bidirectional reflectance, the achievements of bidirectional reflectance of vegetation, such as radiation transfer model, are becoming more and more mature. Geometric optics model, hybrid model and computer simulation model are widely accepted at home and abroad. In the field of vegetation remote sensing, the bidirectional reflectance of vegetation is always the theoretical basis of vegetation multi-angle remote sensing. Due to the complexity of vegetation structure, the limitation of experimental observation instruments and satellite data, and the self-adaptability of the model, it is difficult to achieve the ideal precision in the study of the bidirectional reflectance of vegetation. Especially for trees with larger bodies, it is more difficult to accurately calculate the canopy bidirectional reflectance factor (BRFs) by minimizing abstract simplification according to the true growth structure of trees. In this paper, the radiance model is used to simulate and analyze the two dimensional reflection characteristics of the canopy based on the 3D simulation of the tree real structure scene. The emissivity model consists of two parts: one is to simulate 3D real scene based on L- system, the other is to use radiance method to simulate canopy BRF. The main contents of this paper are as follows: the radiance model of vegetation canopy (RGM) is selected as a tool to simulate the bidirectional reflectivity factors in the main plane and vertical direction of the sun. The input parameters include three dimensional structure file, spectral file, solar and sky definition file, soil file, temperature field file, etc. The BRF values of tree canopy in four bands of visible light and near infrared are calculated. In order to study the effect of model parameters on canopy BRF, different components, leaf structure, solar position, scene parameters (such as field of view, sky light ratio) were simulated. The canopy BRFs of each band were analyzed under the condition of underlying surface type. The results show that when the model parameters vary, the BRF of the canopy will show different changes, such as the increase of the leaf area index, the decrease of the corresponding BRF value, the change of solar zenith angle will cause the hot spot of BRF in the canopy to move, the larger the angle of view, the greater the angle of view. The weaker the hot spot effect is, the lower the canopy BRF is, and the higher the ratio of diffuse light in the sky is, the lower the type of underlying surface is, the corresponding change of canopy BRF will occur. Based on the above conclusions, the extended L- system is used to simulate the 3D scene of trees in the field, and then the canopy BRFs of the whole scene are calculated and verified with the measured canopy BRF data. The results show that the average correlation coefficient between the simulated and measured values of the canopy BRF is more than 0.7, which indicates that the simulated calculation of the canopy BRF based on the RGM model is more accurate, and the reliability of the experiment is verified.
【學(xué)位授予單位】：吉林大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：S758

【參考文獻(xiàn)】

相關(guān)期刊論文 前1條

1 李小文;地物的二向性反射和方向譜特征[J];環(huán)境遙感;1989年01期

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本文編號：1883852