Modeling Continuous Scaling of NDVI Based on Fractal Theory
LUAN Hai-jun1, 2, TIAN Qing-jiu1, 2*, YU Tao3, HU Xin-li3, HUANG Yan1, 2, DU Ling-tong1, 2, ZHAO Li-min3, WEI Xi4, HAN Jie3, ZHANG Zhou-wei5, LI Shao-peng6
1. International Institute for Earth System Science, Nanjing University, Nanjing 210093, China 2. Jiangsu Provincial Key Laboratory of Geographic Information Science and Technology, Nanjing University, Nanjing 210093, China 3. State Key Laboratory of Remote Sensing Science, Institute of Remote Sensing Applications of Chinese Academy of Sciences, Beijing 100101, China 4. School of Automation, University of Electronic Science and Technology of China, Chengdu 611731, China 5. School of Earth and Space Sciences, Peking University, Beijing 100871, China 6. College of Grassland and Environment Sciences, Xinjiang Agricultural University, Urumqi 830052, China
摘要： 尺度效应是遥感领域的一个非常重要的科学问题。定量遥感尺度转换研究可用于解决如定量遥感反演产品真实性检验等诸多颇具挑战性的问题。传统升尺度转换研究方法无法得到连续空间尺度上反演量的变化特性;且面临不同传感器间几何、光谱等特性参数校正问题的干扰，尺度转换研究精度受到影响。为此，基于分形理论利用单一传感器影像解决这些问题。基于Enhanced Thematic Mapper Plus (ETM+)数据，以NDVI(利用其地表辐亮度计算模型)为研究对象，建立了一个可参考的反演量连续空间尺度转换模型研究流程。结果表明：(1)NDVI升尺度转换中存在尺度效应，且此效应可由尺度转换分形模型定量描述;(2)此分形模型适用于NDVI产品的真实性检验中。这表明分形作为一种有效的方法，可用于定量遥感尺度转换研究中。
关键词：定量遥感;空间尺度转换;连续;分形;NDVI;ETM+;真实性检验
Abstract：Scale effect was one of the very important scientific problems of remote sensing. The scale effect of quantitative remote sensing can be used to study retrievals’ relationship between different-resolution images, and its research became an effective way to confront the challenges, such as validation of quantitative remote sensing products et al. Traditional up-scaling methods cannot describe scale changing features of retrievals on entire series of scales; meanwhile, they are faced with serious parameters correction issues because of imaging parameters’ variation of different sensors, such as geometrical correction, spectral correction, etc. Utilizing single sensor image, fractal methodology was utilized to solve these problems. Taking NDVI(computed by land surface radiance) as example and based on Enhanced Thematic Mapper Plus (ETM+) image, a scheme was proposed to model continuous scaling of retrievals. Then the experimental results indicated that: (a) For NDVI, scale effect existed, and it could be described by fractal model of continuous scaling; (2) The fractal method was suitable for validation of NDVI. All of these proved that fractal was an effective methodology of studying scaling of quantitative remote sensing.
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