Wheat Lodging Area Recognition Method Based on Different Resolution UAV Multispectral Remote Sensing Images
Received date: 2023-04-27
Online published: 2023-06-30
Supported by
Henan Province Science and Technology Research and Development Program Joint Fund Advantage Discipline Cultivation Project (222301420104)
[Objective] To quickly and accurately assess the situation of crop lodging disasters, it is necessary to promptly obtain information such as the location and area of the lodging occurrences. Currently, there are no corresponding technical standards for identifying crop lodging based on UAV remote sensing, which is not conducive to standardizing the process of obtaining UAV data and proposing solutions to problems. This study aims to explore the impact of different spatial resolution remote sensing images and feature optimization methods on the accuracy of identifying wheat lodging areas. [Methods] Digital orthophoto images (DOM) and digital surface models (DSM) were collected by UAVs with high-resolution sensors at different flight altitudes after wheat lodging. The spatial resolutions of these image data were 1.05, 2.09, and 3.26 cm. A full feature set was constructed by extracting 5 spectral features, 2 height features, 5 vegetation indices, and 40 texture features from the pre-processed data. Then three feature selection methods, ReliefF algorithm, RF-RFE algorithm, and Boruta-Shap algorithm, were used to construct an optimized subset of features at different flight altitudes to select the best feature selection method. The ReliefF algorithm retains features with weights greater than 0.2 by setting a threshold of 0.2; the RF-RFE algorithm quantitatively evaluated the importance of each feature and introduces variables in descending order of importance to determine classification accuracy; the Boruta-Shap algorithm performed feature subset screening on the full feature set and labels a feature as green when its importance score was higher than that of the shaded feature, defining it as an important variable for model construction. Based on the above-mentioned feature subset, an object-oriented classification model on remote sensing images was conducted using eCognition9.0 software. Firstly, after several experiments, the feature parameters for multi-scale segmentation in the object-oriented classification were determined, namely a segmentation scale of 1, a shape factor of 0.1, and a tightness of 0.5. Three object-oriented supervised classification algorithms, support vector machine (SVM), random forest (RF), and K nearest neighbor (KNN), were selected to construct wheat lodging classification models. The Overall classification accuracy and Kappa coefficient were used to evaluate the accuracy of wheat lodging identification. By constructing a wheat lodging classification model, the appropriate classification strategy was clarified and a technical path for lodging classification was established. This technical path can be used for wheat lodging monitoring, providing a scientific basis for agricultural production and improving agricultural production efficiency. [Results and Discussions] The results showed that increasing the altitude of the UAV to 90 m significantly improved flight efficiency of wheat lodging areas. In comparison to flying at 30 m for the same monitoring range, data acquisition time was reduced to approximately 1/6th, and the number of photos needed decreased from 62 to 6. In terms of classification accuracy, the overall classification effect of SVM is better than that of RF and KNN. Additionally, when the image spatial resolution varied from 1.05 to 3.26 cm, the full feature set and all three optimized feature subsets had the highest classification accuracy at a resolution of 1.05 cm, which was better than at resolutions of 2.09 and 3.26 cm. As the image spatial resolution decreased, the overall classification effect gradually deteriorated and the positioning accuracy decreased, resulting in poor spatial consistency of the classification results. Further research has found that the Boruta-Shap feature selection method can reduce data dimensionality and improve computational speed while maintaining high classification accuracy. Among the three tested spatial resolution conditions (1.05, 2.09, and 3.26 cm), the combination of SVM and Boruta-Shap algorithms demonstrated the highest overall classification accuracy. Specifically, the accuracy rates were 95.6%, 94.6%, and 93.9% for the respective spatial resolutions. These results highlighted the superior performance of this combination in accurately classifying the data and adapt to changes in spatial resolution. When the image resolution was 3.26 cm, the overall classification accuracy decreased by 1.81% and 0.75% compared to 1.05 and 2.09 cm; when the image resolution was 2.09 cm, the overall classification accuracy decreased by 1.06% compared to 1.05 cm, showing a relatively small difference in classification accuracy under different flight altitudes. The overall classification accuracy at an altitude of 90 m reached 95.6%, with Kappa coefficient of 0.914, meeting the requirements for classification accuracy. [Conclusions] The study shows that the object-oriented SVM classifier and the Boruta-Shap feature optimization algorithm have strong application extension advantages in identifying lodging areas in remote sensing images at multiple flight altitudes. These methods can achieve high-precision crop lodging area identification and reduce the influence of image spatial resolution on model stability. This helps to increase flight altitude, expand the monitoring range, improve UAV operation efficiency, and reduce flight costs. In practical applications, it is possible to strike a balance between classification accuracy and efficiency based on specific requirements and the actual scenario, thus providing guidance and support for the development of strategies for acquiring crop lodging information and evaluating wheat disasters.
Key words: wheat lodging; UAV; flight altitude; feature selection; classification model; SVM; RF; KNN
WEI Yongkang , YANG Tiancong , DING Xinyao , GAO Yuezhi , YUAN Xinru , HE Li , WANG Yonghua , DUAN Jianzhao , FENG Wei . Wheat Lodging Area Recognition Method Based on Different Resolution UAV Multispectral Remote Sensing Images[J]. Smart Agriculture, 2023 , 5(2) : 56 -67 . DOI: 10.12133/j.smartag.SA202304014
1 | 中华人民共和国国家统计局. 国家数据[EB/OL]. (2021-12-06)[2023-01-29] . |
2 | ISLAM M S, PENG S B, VISPERAS R M, et al. Lodging-related morphological traits of hybrid rice in a tropical irrigated ecosystem[J]. Field crops research, 2007, 101(2): 240-248. |
3 | BERRY P M, STERLING M, BAKER C J, et al. A calibrated model of wheat lodging compared with field measurements[J]. Agricultural and forest meteorology, 2003, 119(3/4): 167-180. |
4 | CHAUHAN S, DARVISHZADEH R, BOSCHETTI M, et al. Remote sensing-based crop lodging assessment: Current status and perspectives[J]. ISPRS journal of photogrammetry and remote sensing, 2019, 151: 124-140. |
5 | 李宗南, 陈仲新, 任国业, 等. 基于Worldview-2影像的玉米倒伏面积估算[J]. 农业工程学报, 2016, 32(2): 1-5. |
LI Z N, CHEN Z X, REN G Y, et al. Estimation of maize lodging area based on Worldview-2 image[J]. Transactions of the Chinese society of agricultural engineering, 2016, 32(2): 1-5. | |
6 | 晏磊, 廖小罕, 周成虎, 等. 中国无人机遥感技术突破与产业发展综述[J]. 地球信息科学学报, 2019, 21(4): 476-495. |
YAN L, LIAO X H, ZHOU C H, et al. The impact of UAV remote sensing technology on the industrial development of China: A review[J]. Journal of geo-information science, 2019, 21(4): 476-495. | |
7 | TIAN M L, BAN S T, YUAN T, et al. Assessing rice lodging using UAV visible and multispectral image[J]. International journal of remote sensing, 2021, 42(23): 8840-8857. |
8 | 赵静, 潘方江, 兰玉彬, 等. 无人机可见光遥感和特征融合的小麦倒伏面积提取[J]. 农业工程学报, 2021, 37(3): 73-80. |
ZHAO J, PAN F J, LAN Y B, et al. Wheat lodging area extraction using UAV visible light remote sensing and feature fusion[J]. Transactions of the Chinese society of agricultural engineering, 2021, 37(3): 73-80. | |
9 | SUN Q, SUN L, SHU M Y, et al. Monitoring maize lodging grades via unmanned aerial vehicle multispectral image[J]. Plant phenomics, 2019, 2019: ID 5704154. |
10 | FLORES P, 张昭. 基于无人机图像以及不同机器学习和深度学习模型的小麦倒伏率检测[J]. 智慧农业(中英文), 2021, 3(2): 23-34. |
FLORES P, ZHANG Z. Wheat lodging ratio detection based on UAS imagery coupled with different machine learning and deep learning algorithms[J]. Smart agriculture, 2021, 3(2): 23-34. | |
11 | 黄艳伟, 朱红雷, 郭宁戈, 等. 基于无人机多光谱影像的冬小麦倒伏提取适宜空间分辨率研究[J]. 麦类作物学报, 2021, 41(2): 254-261. |
HUANG Y W, ZHU H L, GUO N G, et al. Study on the suitable resolution of winter wheat lodging extraction based on UAV multispectral image[J]. Journal of triticeae crops, 2021, 41(2): 254-261. | |
12 | YU J, CHENG T, CAI N, et al. Wheat lodging extraction using Improved_Unet network[J]. Frontiers in plant science, 2022, 13: ID 1009835. |
13 | GUYON I, ELISSEEFF A. An introduction to variable and feature selection[J]. Journal of machine learning research, 2003, 3: 1157-1182. |
14 | CHAUHAN S, DARVISHZADEH R, BOSCHETTI M, et al. Discriminant analysis for lodging severity classification in wheat using RADARSAT-2 and Sentinel-1 data[J]. ISPRS journal of photogrammetry and remote sensing, 2020, 164: 138-151. |
15 | INOUE Y, SAKAIYA E, ZHU Y, et al. Diagnostic mapping of canopy nitrogen content in rice based on hyperspectral measurements[J]. Remote sensing of environment, 2012, 126: 210-221. |
16 | HUNT E R, DAUGHTRY C S T, EITEL J U H, et al. Remote sensing leaf chlorophyll content using a visible band index[J]. Agronomy journal, 2011, 103(4): 1090-1099. |
17 | AHAMED T, TIAN L, ZHANG Y, et al. A review of remote sensing methods for biomass feedstock production[J]. Biomass and bioenergy, 2011, 35(7): 2455-2469. |
18 | S S K P, S D V. Extraction of texture features using GLCM and shape features using connected regions[J]. International journal of engineering and technology, 2016, 8(6): 2926-2930. |
19 | 支俊俊, 董娅, 鲁李灿, 等. 基于无人机RGB影像的玉米种植信息高精度提取方法[J]. 农业工程学报, 2021, 37(18): 48-54. |
ZHI J J, DONG Y, LU L C, et al. High-precision extraction method for maize planting information based on UAV RGB images[J]. Transactions of the Chinese society of agricultural engineering, 2021, 37(18): 48-54. | |
20 | AGJEE N H, ISMAIL R, MUTANGA O. Identifying relevant hyperspectral bands using Boruta: A temporal analysis of water hyacinth biocontrol[J]. Journal of applied remote sensing, 2016, 10(4): ID 042002. |
21 | GHOSH I, CHAUDHURI T D. Integrating Navier-Stokes equation and neoteric iForest-BorutaShap-Facebook's prophet framework for stock market prediction: An application in Indian context[J]. Expert systems with applications, 2022, 210: ID 118391. |
22 | 王吉川, 刘艺. 特征选择稳定性方法研究[J]. 数字技术与应用, 2021, 39(9): 19-21. |
WANG J C, LIU Y. Research on methods for feature selection stability[J]. Digital technology & application, 2021, 39(9): 19-21. | |
23 | 崔鸿雁, 徐帅, 张利锋, 等. 机器学习中的特征选择方法研究及展望[J]. 北京邮电大学学报, 2018, 41(1): 1-12. |
CUI H Y, XU S, ZHANG L F, et al. The key techniques and future vision of feature selection in machine learning[J]. Journal of Beijing university of posts and telecommunications, 2018, 41(1): 1-12. | |
24 | 尚志刚, 董永慧, 李蒙蒙, 等. 基于偏最小二乘回归的鲁棒性特征选择与分类算法[J]. 计算机应用, 2017, 37(3): 871-875. |
SHANG Z G, DONG Y H, LI M M, et al. Robust feature selection and classification algorithm based on partial least squares regression[J]. Journal of computer applications, 2017, 37(3): 871-875. | |
25 | 刘艺, 曹建军, 刁兴春, 等. 特征选择稳定性研究综述[J]. 软件学报, 2018, 29(9): 2559-2579. |
LIU Y, CAO J J, DIAO X C, et al. Survey on stability of feature selection[J]. Journal of software, 2018, 29(9): 2559-2579. | |
26 | 周小成, 郑磊, 黄洪宇. 基于多特征优选的无人机可见光遥感林分类型分类[J]. 林业科学, 2021, 57(6): 24-36. |
ZHOU X C, ZHENG L, HUANG H Y. Classification of forest stand based on multi-feature optimization of UAV visible light remote sensing[J]. Scientia silvae sinicae, 2021, 57(6): 24-36. | |
27 | 刘良云, 王纪华, 宋晓宇, 等. 小麦倒伏的光谱特征及遥感监测[J]. 遥感学报, 2005, 9(3): 323-327. |
LIU L Y, WANG J H, SONG X Y, et al. The canopy spectral features and remote sensing of wheat lodging[J]. Journal of remote sensing, 2005, 9(3): 323-327. | |
28 | 李广, 张立元, 宋朝阳, 等. 小麦倒伏信息无人机多时相遥感提取方法[J]. 农业机械学报, 2019, 50(4): 211-220. |
LI G, ZHANG L Y, SONG C Y, et al. Extraction method of wheat lodging information based on multi-temporal UAV remote sensing data[J]. Transactions of the Chinese society for agricultural machinery, 2019, 50(4): 211-220. |
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