杨颖频, 吴志峰, 骆剑承, 黄启厅, 张冬韵, 吴田军, 孙营伟, 曹峥, 董文, 刘巍. 时空协同的地块尺度作物分布遥感提取[J]. 农业工程学报, 2021, 37(7): 166-174. DOI: 10.11975/j.issn.1002-6819.2021.07.020
    引用本文: 杨颖频, 吴志峰, 骆剑承, 黄启厅, 张冬韵, 吴田军, 孙营伟, 曹峥, 董文, 刘巍. 时空协同的地块尺度作物分布遥感提取[J]. 农业工程学报, 2021, 37(7): 166-174. DOI: 10.11975/j.issn.1002-6819.2021.07.020
    Yang Yingpin, Wu Zhifeng, Luo Jiancheng, Huang Qiting, Zhang Dongyun, Wu Tianjun, Sun Yingwei, Cao Zheng, Dong Wen, Liu Wei. Parcel-based crop distribution extraction using the spatiotemporal collaboration of remote sensing data[J]. Transactions of the Chinese Society of Agricultural Engineering (Transactions of the CSAE), 2021, 37(7): 166-174. DOI: 10.11975/j.issn.1002-6819.2021.07.020
    Citation: Yang Yingpin, Wu Zhifeng, Luo Jiancheng, Huang Qiting, Zhang Dongyun, Wu Tianjun, Sun Yingwei, Cao Zheng, Dong Wen, Liu Wei. Parcel-based crop distribution extraction using the spatiotemporal collaboration of remote sensing data[J]. Transactions of the Chinese Society of Agricultural Engineering (Transactions of the CSAE), 2021, 37(7): 166-174. DOI: 10.11975/j.issn.1002-6819.2021.07.020

    时空协同的地块尺度作物分布遥感提取

    Parcel-based crop distribution extraction using the spatiotemporal collaboration of remote sensing data

    • 摘要: 地块尺度作物分布信息清晰直观地反映了农田位置、空间形态等空间细节和种植类型信息,对精准农业管理、种植补贴发放和农业资源调查等具有重要价值。虽然遥感时空协同思路为地块尺度作物分布提取提供了解决方案,但在农田地块提取和时序特征构建方面尚存在不足。该研究基于遥感时空协同的思路,以Google Earth高空间分辨率影像为底图,利用擅于学习影像视觉特征的D-LinkNet深度学习模型,快速、精准提取农田地块形态;以地块为观测单元,利用Landsat8和Sentinel-2多源遥感的“碎片化”无云数据构建地块时序数据集,基于加权Double-Logistic函数重建地块归一化植被指数(Normalized Difference Vegetation Index,NDVI)时序曲线;提取地块物候特征和多时相光谱特征,经过特征优选和随机森林分类模型构建,开展地块尺度作物分布制图。以广西扶绥县为研究区开展试验,共提取地块43.7万个,边界准确率为84.54%,相较于常规基于多尺度分割的地块提取,基于D-LinkNet的地块提取方法直接排除了非农田地物的干扰,地块形态与现实情况符合度更高;地块NDVI时间序列重建结果能够较好地捕捉作物开始生长、旺盛期、成熟收获期的动态变化趋势;分类特征重要性评价结果显示,红边特征、与时间相关的物候特征在分类中发挥重要作用,当联合物候特征和光谱特征时分类效果最佳;根据特征重要性分析不同特征数量情况下的分类精度,当特征数量大于40维时,作物分类精度和Kappa系数保持稳定,总体分类精度维持在88%左右;对扶绥县地块尺度作物分布进行制图,提取甘蔗地块277 421个、水稻地块33 747个、香蕉地块4 973个、柑橘地块102 055个,分别占农田地块总数的63.48%、7.72%、1.14%、23.35%,种植面积占比分别为69.78%、7.12%、1.71%、18.06%。该研究在理论上构建了遥感时空协同的地块尺度作物分类模型,为大范围、地块尺度作物分布遥感提取提供了实用化方案。

       

      Abstract: Parcel-based classification of crops is paramount to quantify changes in ecological systems and improve management strategies in precision agriculture. Specifically, the obtained location and boundary of farmland together with crop types can contribute to the specific payment of planting subsidies and resource survey. Multi-source high-spatial and temporal resolution satellite images can provide an effective way to realize parcel-based crop mapping. However, some deficiencies still remain in the parcel extraction of farmland and construction of spatiotemporal features. In this present study, a novel model was constructed to implement a parcel-based classification of crops using the spatiotemporal collaborated satellite data with high-spatial and temporal resolution. Four steps were included in a parcel-based crop mapping: 1) A D-LinkNet deep learning model was selected to extract the parcels from the 0.6m high-spatial-resolution Google Earth images; 2) Time series data set was constructed for each parcel using multi-source observations from Landsat 8 and Sentinel-2 satellite, where the tiles with high cloud cover were removed from the images; 3) A weighted Double-Logistic fitting was utilized to reconstruct the parcel-based Normalized Difference Vegetation Index (NDVI) time series for the extraction of phenological parameters, such as the duration of the growth cycle, the time of growth starting and ending, thereby calculating spectral indexes from Landsat8 and Sentinel-2 multispectral data; 4) A Mean Decrease Accuracy (MDA) indicator was used to estimate the feature importance. A field experiment was also conducted to collect the data of crop types for the training of random forest classification model in a parcel-based crop mapping. The Fusui County in Guangxi Zhuang Autonomous Region of China was taken as the study area. There was a relatively complex planting structure in the study area, because it was cloudy and rainy with the rainfall days of about 130-220 d, as well as the diverse and complex topography with a high level and fragmentation. The dominated crops included sugarcane, paddy rice, banana, and orange. The results showed that the farmland parcels were well segmented in the whole images, while the crop distributions of resultant parcels were also well extracted by a D-LinkNet deep learning model, with an edge accuracy of 84.54% and a produce accuracy of 83.06%, compared with the conventional multi-scale segmentation. Phenological features were achieved in the reconstructed NDVI time series of sugarcane, paddy rice, and banana. The NDVI of sugarcane and paddy rice first increased and then decreased significantly. The growth season of sugarcanes started from March to the following March. In addition, the growth season of paddy rice lasted for about 3-4 months, in which there was the most intense change in the NDVI time series. There was a relatively steady state in the reconstructed NDVI time series of evergreen eucalyptus and orange in the whole year. The eucalyptus with high vegetation cover showed high NDVI values during the observation period. The MDA indicator demonstrated that the images captured in summer and autumn were better for the crop classification in the study area. A best performance of classification was achieved to combine the phenological and spectral red-edge features in Sentinel-2 images. The overall accuracy reached 88%, and the accuracy of sugarcane reached over 95% in the study areas. The crop mapping indicated that sugarcane was spatially distributed around the whole study area, including plain and mountainous areas. The planting area of sugarcane accounted for nearly 70%, orange for 18.6%, and paddy rice for 7.12% of farmland. Furthermore, the paddy rice was mostly distributed near the settlement places. Consequently, the Landsat 8 and Sentinel-2 multi-source observations can be expected to successfully extract the phenological features in the parcel-based crop mapping. The finding can provide a series of practical schemes to acquire parcel-based crop distribution.

       

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