基于热点效应的不同株型小麦LAI反演

Inversion of LAI by Considering the Hotspot Effect for Different Geometrical Wheat

针对小麦株型对LAI反演精度的制约,利用地面实测的多角度数据,提出采用热点指数反演高精度的不同株型小麦LAI。通过分析京411紧凑型和中优9507披散型两种株型小麦在红光(670nm)和近红外波段(800和860nm)的二向反射光谱特征,借鉴热暗点指数HDS和归一化热暗点信息指数NDHD,构建了改进的归一化热暗点指数MNDHD和热暗点比值指数HDRI两个新热点指数。将HDS,NDHD,MNDHD和HDRI与NDVI,SR和EVI相乘得到的热点组合指数用于不同株型小麦LAI的反演。分析得出对紧凑型小麦京411,由860nm近红外波段的NDVI与MNDHD和HDRI的组合指数反演的LAI精度分别为0.9431和0.909 2;对披散型小麦中优9507,由800nm近红外波段的SR与HDRI和MNDHD的组合指数获得的LAI反演精度分别为0.964 8和0.895 6。表明基于冠层的热点效应反演不同株型小麦LAI的方法可行,多角度遥感数据在作物结构参数提取方面比常规观测数据更具优势。

Aimed to deal with the limitation of canopy geometry to crop LAI inversion accuracy a new LAI inversion method for different geometrical winter wheat was proposed based on hotspot indices with field-measured experimental data. The present pa- per analyzed bidirectional reflectance characteristics of erective and loose varieties at red （680 nm） and NIR wavelengths（800 nm and 860 nm） and developed modified normalized difference between hotspot and dark-spot （MNDHD） and hotspot and dark-spotratio index（HDRI） using hotspot and dark-spot index（HDS） and normalized difference between hotspot and dark-spot（NDHD） for reference. Combined indices were proposed in the form of the product between HDS, NDHD, MNDHD, HDRI and three or- dinary vegetation indices NDVI, SR and EVI to inverse LAI for erective and loose wheat. The analysis results showed that LAI inversion accuracy of erective wheat Jing411 were 0. 943 1 and 0. 909 2 retrieved from the combined indices between NDVI and MNDHD and HDRI at 860 nm which were better than that of HDS and NDHD, the LAI inversion accuracy of loose wheat Zhongyou9507 were 0. 964 8 and 0. 895 6 retrieved from the combined indices between SR and HDRI and MNDHD at 800 nm which were also higher than that of HDS and NDHD. It was finally concluded that the combined indices between hotspot-signa- ture indices and ordinary vegetation indices were feasible enough to inverse LAI for different crop geometrical wheat and multi- angle remote sensing data was much more advantageous than perpendicular observation data to extract crop structural parame- ters.