牛乾坤, 刘浏, 黄冠华, 程湫雅, 程泳铭. 基于GEE和机器学习的河套灌区复杂种植结构识别[J]. 农业工程学报, 2022, 38(6): 165-174. DOI: 10.11975/j.issn.1002-6819.2022.06.019
    引用本文: 牛乾坤, 刘浏, 黄冠华, 程湫雅, 程泳铭. 基于GEE和机器学习的河套灌区复杂种植结构识别[J]. 农业工程学报, 2022, 38(6): 165-174. DOI: 10.11975/j.issn.1002-6819.2022.06.019
    Niu Qiankun, Liu Liu, Huang Guanhua, Cheng Qiuya, Cheng Yongming. Extraction of complex crop structure in the Hetao Irrigation District of Inner Mongolia using GEE and machine learning[J]. Transactions of the Chinese Society of Agricultural Engineering (Transactions of the CSAE), 2022, 38(6): 165-174. DOI: 10.11975/j.issn.1002-6819.2022.06.019
    Citation: Niu Qiankun, Liu Liu, Huang Guanhua, Cheng Qiuya, Cheng Yongming. Extraction of complex crop structure in the Hetao Irrigation District of Inner Mongolia using GEE and machine learning[J]. Transactions of the Chinese Society of Agricultural Engineering (Transactions of the CSAE), 2022, 38(6): 165-174. DOI: 10.11975/j.issn.1002-6819.2022.06.019

    基于GEE和机器学习的河套灌区复杂种植结构识别

    Extraction of complex crop structure in the Hetao Irrigation District of Inner Mongolia using GEE and machine learning

    • 摘要: 河套灌区作为中国重要的商品粮油生产基地,准确快速地获取主要作物空间分布对灌区的农业可持续发展具有重要意义。然而,河套灌区土壤盐渍化严重,作物分布破碎散乱,生育期前后紧邻的作物在遥感影像中难以区分。因此,基于Google Earth Engine(GEE)云计算平台,采用Sentinel-2遥感数据提取作物种植结构,通过引入GlobeLand30地物分类数据集、红边植被特征和作物纹理特征,利用随机森林、支持向量机、朴素贝叶斯和分类回归树4种分类器,探讨了不同分类特征及分类器组合对分类精度的影响。结果表明,使用全部特征波段时,随机森林的分类效果优于另外3种分类算法,灌区平均总体精度达到81%,Kappa系数达到0.68;在作物空间分布提取中,光谱特征对分类精度起决定性作用,基于红边波段计算得到的植被指数比其他常用遥感植被指数更有优势;进行波段优选后的光谱、植被和纹理特征方案是平均分类精度最高的组合,平均精度为86%。研究结果可为复杂种植结构地区准确快速获取农作物空间分布信息提供新的思路和可靠的参考方法。

       

      Abstract: Abstract: Hetao Irrigation District (HTID) has been the largest self-flowing irrigation district with one water intake in Asia, serving an important commercial grain and oil production base in China. The annual grain production in the HTID reached 2.55 million tons in 2018, accounting for 3.9‰ of the total crop cultivation area in China. Therefore, accurate and rapid extraction of crop structure can be of great practical significance in agricultural production for the food security of the HTID. However, it is difficult to distinguish the pixels of major crops in the remote sensing images, due to the severe soil salinization, fragmented and scattered crop distribution, as well as the same crop with the different spectrum of various crops. Moreover, there are the close growth periods of major crops in the HTID, which can mix the elements in the images. In this study, Sentinel-2 high-resolution remote sensing images and the GlobeLand30 dataset were used to extract the crop planting structure of the HTID using the Google Earth Engine cloud computing platform. Nearly 1 200 sample points were filtrated using the OTSU algorithm and Google Earth visual interpretation. The features of spectra, frequently-used vegetation, red-edge vegetation, and crop texture were input into four classifiers, including the Random Forest (RF), Support Vector Machine (SVM), Naive Bayes (NB), Classification and Regression Tree (CART). The Overall Accuracy (OA) and Kappa coefficient were used to evaluate the performances of model for the extraction of crop planting structure. Firstly, the impacts of classification features and classifiers combinations on the classification accuracy were explored to identify the classifier with the highest classification accuracy. Then, the feature optimization was performed on the five irrigation sub-districts using out-of-bag error rates for each irrigation sub-district. Finally, the optimal classifier and feature combinations were achieved to derive the cropping structure of four crops in the HTID in 2018. The results show that the RF classifier presented the highest classification accuracy using all feature bands, where the average OA of the HTID (81%) was 6 percentage points and 11 percentage points higher than that of the SVM and NB classifier, respectively. The Kappa coefficient reached 0.68, which was much higher than the rest. Furthermore, the importance of feature bands filtered by the RF was ranked first for the spectral features, the second for the vegetation features, and last for the gray texture features. The indexes were calculated using red-edge bands, indicating the better performance over the other commonly-used remote sensing vegetation indices in crop recognition. In addition, the feature-optimized scheme was the combination with the highest average OA of 86% and Kappa coefficient of 0.78, while the scheme containing 25 bands of spectral, vegetation and texture features presented an OA of 85% and Kappa coefficient of 0.75. Therefore, the new sights can be offered for extracting crop spatial distribution using remote sensing cloud computing platform in complex planting structure area. The finding can provide a strong reference to adjust the agricultural production structure, and further formulate the food macro-control policies in the Hetao Irrigation District.

       

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