Sentinel-2光学影像特征在东北地区水稻株高反演中的应用潜力研究

Application potential of Sentinel-2 optical image features for rice plant height inversion in Northeast China

  • 摘要: 水稻株高是反映水稻长势的一个重要指标。当前的株高遥感反演方法受数据的成本和更新频率的制约, 无法满足大范围、多频次的农作物株高业务化监测需求, 仍需充分挖掘高时空分辨率光学卫星数据的潜力。选择东北地区水稻为研究对象, 采用2022年和2023年的株高实测数据, 以Sentinel-2为数据源构建光学影像基础特征集。在此基础上, 首先利用统计分析初步探究各特征对株高的敏感性, 然后利用随机森林算法和极限梯度提升算法构建多个不同特征组合的回归模型, 同时结合特征递归消除和重要性排序方法, 分别对单特征、不同类别特征的重要性进行分析, 并总体评估Sentinel-2影像特征的应用潜力。最终, 全特征优选后的随机森林模型达到最高估算精度, R2=0.857, RMSE=8.395 cm。对比分析发现, 单个特征中, 植被水分指数以及蓝光波段表现出了极高的重要性, 红边特征、红光波段、绿光波段以及纹理均值也均被选入最优特征集, 具有一定的株高监测能力; 不同类别的光学特征中, 植被指数特征比反射率特征更重要, 纹理特征单独应用时难以达到较高的估算精度, 但能够作为补充信息, 与另外两类特征组合提高估算精度。与前人研究相比, Sentinel-2数据株高估算精度相当, 但能实现快速、多期、大范围的株高估算, 具有良好的业务化应用潜力。

     

    Abstract: Plant height is an important indicator of the rice growth status. Current remote sensing retrieval methods for plant height are limited by data cost and update frequency and cannot meet the requirements of large-scale and multi-frequency operational monitoring of crop plant height; therefore, there is still a need to fully explore the potential of high spatial and temporal resolution optical satellite data. Choosing rice in the northeastern region of China as the research subject, measured plant height data from 2022 and 2023 were used, and an optical image-based feature set was constructed using Sentinel-2 data. Based on this, statistical analysis was used to explore the sensitivity of each feature to plant height. Multiple regression models with different feature combinations were then constructed using the random forest and extreme gradient boosting algorithms. Simultaneously, feature recursive elimination and importance-ranking methods were employed to analyze the importance of single features and different categories of features. Finally, the overall potential of Sentinel-2 images was evaluated. Finally, the random forest model with all optimized features achieved the highest estimation accuracy, with R2=0.857 and RMSE=8.395 cm. Comparative analysis revealed that among the individual features, the vegetation water index and blue band were highly important. Red edge features, red bands, green bands, and texture means were also selected into the optimal feature set, demonstrating certain plant height monitoring capabilities. Among the different categories of optical features, the vegetation index features were more important than the reflectance features. When texture features were applied alone, it was difficult to achieve a high estimation accuracy, but they could serve as supplementary information when combined with the other two categories of features to improve the estimation accuracy. Compared with previous studies, the accuracy of plant height estimation using Sentinel-2 data is comparable; however, it enables rapid, multi-period, and large-scale estimation of plant height, showing good application potential.

     

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