徐云飞, 程 琦, 魏祥平, 杨斌, 夏沙沙, 芮婷婷, 张世文. 变异系数法结合优化神经网络的无人机冬小麦长势监测[J]. 农业工程学报, 2021, 37(20): 71-80. DOI: 10.11975/j.issn.1002-6819.2021.20.008
    引用本文: 徐云飞, 程 琦, 魏祥平, 杨斌, 夏沙沙, 芮婷婷, 张世文. 变异系数法结合优化神经网络的无人机冬小麦长势监测[J]. 农业工程学报, 2021, 37(20): 71-80. DOI: 10.11975/j.issn.1002-6819.2021.20.008
    Xu Yunfei, Cheng Qi, Wei Xiangping, Yang bin, Xia Shasha, Rui Tingting, Zhang Shiwen. Monitoring of winter wheat growth under UAV using variation coefficient method and optimized neural network[J]. Transactions of the Chinese Society of Agricultural Engineering (Transactions of the CSAE), 2021, 37(20): 71-80. DOI: 10.11975/j.issn.1002-6819.2021.20.008
    Citation: Xu Yunfei, Cheng Qi, Wei Xiangping, Yang bin, Xia Shasha, Rui Tingting, Zhang Shiwen. Monitoring of winter wheat growth under UAV using variation coefficient method and optimized neural network[J]. Transactions of the Chinese Society of Agricultural Engineering (Transactions of the CSAE), 2021, 37(20): 71-80. DOI: 10.11975/j.issn.1002-6819.2021.20.008

    变异系数法结合优化神经网络的无人机冬小麦长势监测

    Monitoring of winter wheat growth under UAV using variation coefficient method and optimized neural network

    • 摘要: 高效、快速、准确获取冬小麦长势信息在农业发展和经营决策中具有重要作用。该研究以冬小麦为对象,开展无人机冬小麦长势监测,获取冬小麦生物量、株高、叶绿素含量和植株含水率数据,基于变异系数法(Coefficient of Variation Method,CV)构建综合长势监测指标(Comprehensive Growth Monitoring Indicators,CGMICV),通过16种植被指数与CGMICV进行相关性分析,计算植被指数间的方差膨胀因子,筛选最优植被指数作为模型输入变量,采用偏最小二乘(Partial Least Squares Regression,PLSR)、随机森林(Random Forest,RF)、反向传播神经网络(Back Propagation Neural Networks,BPNN)及遗传算法(Genetic Algorithm,GA)优化的BPNN模型建立冬小麦长势反演模型,结合评价指标获得冬小麦最优长势反演模型,最终得到研究区冬小麦长势空间分布信息。研究结果表明:以变异系数法得到的冬小麦CGMICV相关性比单一指标的相关性有不同程度的提高;利用变异系数法结合BPNN得到的冬小麦长势最佳反演模型CGMICV-BPNN,其决定系数R2可达0.71,模型精度较传统赋权法构建的CGMImean-BPNN模型提高了26.79%;采用GA优化后的BPNN模型的不稳定显著下降,其平均相对误差中位数下降了22.22%,决定系数R2也有所提高;研究区内半数以上的冬小麦长势集中于第Ⅲ等级,其所占比例为55.83%,其次集中于第Ⅰ等级,其所占比例为36.08%,研究区冬小麦整体长势较为稳定。研究结果可为冬小麦长势监测及区域作物生产监测提供重要参考。

       

      Abstract: Abstract: Accurate and rapid acquisition of growth information has been one of the most important steps for winter wheat production in agricultural development and management decision-making. Most previous achievements focus on the monitoring of crop growth using Unmanned Aerial Vehicle (UAV) in recent years. Among them, the most extensive reports can be chlorophyll, biomass, plant height, and water content. Taking the winter wheat as the research object, this study aims to monitor the growth characteristics of the plant under a UAV using the Coefficient of Variation (CV) and optimized neural network. A Comprehensive Growth Monitoring Indicators (CGMICV) was also considered to integrate with the CV and different indexes, including the biomass, plant height, plant water, and chlorophyll content. In addition, the multispectral data of UAV was obtained, such as red, green, red edge, and near-infrared band. Subsequently, 16 multispectral vegetation indices were selected to analyze the correlation between the vegetation index and CGMICV, according to the characteristic band range of crops. The variance expansion factor was then calculated to screen the input variables of the model. Finally, six optimal vegetation indices were selected as the input variables of the model. As such, the growth model of winter wheat was established using the Partial Least Squares Regression (PLSR), Random Forest (RF), and Back Propagation Neural Networks (BPNN). Correspondingly, an optimal growth inversion model of winter wheat was achieved, including the determining coefficient (R2), Root Mean Square Error (RMSE), and Mean Absolute Error (MAE), according to the combined evaluation indexes. More importantly, Genetic Algorithm (GA) was utilized to optimize the growth inversion model for the whole region. The spatial distribution of winter wheat growth was then obtained in the study area. The results showed that the correlation between the CGMICV of winter wheat was much higher than that of the single index, where the most outstanding one was the Soil Plant Analysis Development (SPAD). The best inversion model of CGMICV-BPNN was achieved for the growth of winter wheat, where a determination coefficient R2 was 0.71, and the accuracy of the model was 26.79% higher than that of the traditional one (CGMImean-BPNN), fully meeting the current accuracy for the comprehensive monitoring of crop growth. The stability of the optimized CGMICV-GA-BPNN model was significantly better than that of CGMICV -BPNN. the mean relative error median was reduced by 22.22%, and the determination coefficient R2 was also increased. The CGMICV-GA-BPNN model was then applied for the growth distribution map of winter wheat in the whole study area. More than half of winter wheat was concentrated in grade III, followed by grade I. It inferred that the overall growth of winter wheat was relatively stable. At the same time, it was also found that the optimized CGMICV -BPNN model can be used to integrate the multiple growth factors of winter wheat, indicating a better performance to quantify the growth monitoring of regional winter wheat. The findings can provide an important reference for the growth monitoring of winter wheat in crop production.

       

    /

    返回文章
    返回