中国农业科学 ›› 2022, Vol. 55 ›› Issue (20): 3926-3938.doi: 10.3864/j.issn.0578-1752.2022.20.005

• 耕作栽培·生理生化·农业信息技术 • 上一篇    下一篇

基于无人机多光谱影像的小麦封垄前种植行识别方法改进

马啸1,2(),陈鹏飞1,3()   

  1. 1中国科学院地理科学与资源研究所/资源与环境信息系统国家重点实验室,北京 100101
    2中国科学院大学,北京 100049
    3国家科技资源共享服务平台国家地球系统科学数据中心,北京 100101
  • 收稿日期:2021-12-10 接受日期:2022-02-28 出版日期:2022-10-16 发布日期:2022-10-24
  • 通讯作者: 陈鹏飞
  • 作者简介:马啸,E-mail: maxiao20@mails.ucas.ac.cn
  • 基金资助:
    国家自然科学基金(41871344);中国科学院战略先导科技专项(XDA23100100);高分辨率对地观测系统重大专项(21-Y20B01-9001-19/22);国家科技基础条件平台项目(2005DKA32300)

Improvement of Row Detection Method Before Wheat Canopy Closure Using Multispectral Images of UAV Image

MA Xiao1,2(),CHEN PengFei1,3()   

  1. 1Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences/State Key Laboratory of Resources and Environment Information System, Beijing 100101
    2University of Chinese Academy of Science, Beijing 100049
    3National Earth System Science Data Center, National Science and Technology Infrastructure of China, Beijing 100101
  • Received:2021-12-10 Accepted:2022-02-28 Online:2022-10-16 Published:2022-10-24
  • Contact: PengFei CHEN

摘要:

【目的】 为实现小麦精准管理,准确识别其种植行位置具有重要意义。本研究分别针对传统Hough变换法和绿色像元累积法存在的缺陷进行改进,并对改进前、后不同方法在小麦种植行识别上的精度进行对比分析,为小麦种植行精准提取提供技术支撑。【方法】 本研究开展了小麦水、氮耦合试验,在小麦拔节前期,基于四旋翼无人机携带RedEdge M传感器获取小麦不同生长条件下多光谱影像。基于上述数据,首先采用超绿超红差分指数和Otsu方法对影像分割、分类,获取植被/土壤二值图;其次,采用3×1线型模板进行形态学开运算,降低边界不规则度并去除噪音;然后,结合无人机影像中小麦种植行排布特点,分别针对传统Hough变换法的峰值检测过程和绿色像素累积法的角度检测过程进行优化,提出改进的小麦种植行识别方法;最后,分别将两种方法改进前、后的识别结果与目视解译种植行位置结果进行对比,基于检出率和作物行识别精度(crop row detection accuracy,CRDA)评价4种方法的优劣。【结果】 采用超绿超红差分指数与Otsu方法可以很好对植被/土壤进行分类,分类结果的总体精度达到93.75%,Kappa系数为0.87;形态学运算可以很好地去除图像噪声,减少后期种植行识别误差;改进后Hough变换法通过利用先验知识对峰值检测范围进行约束,有效提升了种植行检测精度,种植行平均检出率从30%提升至67%,CRDA平均值从0.22提升至0.44;改进后绿色像元累积法通过考察整幅影像的绿色像元累积特征,有效提升角度检测精度,种植行平均检出率从14%提升至93%,CRDA平均值从0.12提升至0.69;4种方法的识别精度从高到低依次为改进后绿色像元累积法、改进后Hough变换法、改进前Hough变换法、改进前绿色像元累积法。【结论】 本研究较好地改进了传统种植行识别方法,为种植密度大、行间距小的小麦种植行识别提供了技术支撑。

关键词: 小麦, 种植行, Hough变换法, 绿色像元累积法, 无人机影像

Abstract:

【Objective】In order to make precise management of wheat, it is of great significance to accurately identify the location of its rows. In this study, the aim was to improve the traditional Hough transform-based methods and the green pixel accumulation- based methods respectively, and then to analyze the different methods before and after the improvement for wheat row detection, so as to provide the technical support for accurate detection of wheat rows.【Method】A wheat water-nitrogen coupling experiment was established. During the early jointing stage, the multispectral images of wheat under different growth conditions was obtained by the RedEdge M sensors mounted on a four rotor unmanned aerial vehicle (UAV). First, based on these data, these images of the excess green minus excess red (ExGR) index were calculated, and then the Otsu method was performed on it to classify image pixels into vegetation and soil. Second, 3×1 line template was used for morphological opening operation to reduce boundary irregularity and remove noise. Third, according to the characteristics of the wheat rows in the image, the modified wheat row extraction methods were proposed based on the optimization of the peak detection process of the traditional Hough transform-based method and the angel detection process of the traditional green pixel accumulation-based method, respectively. Finally, the detection results before and after improving the two methods were compared with the result of visually interpreted wheat rows, and their performances were evaluated by using the detection rate and crop row detection accuracy (CRDA). 【Result】The combination of the ExGR index and OTSU method could accurately identify the vegetation pixels and soil pixels automatically, and the overall accuracy was 93.75% and the Kappa was 0.87. The morphological opening operation could remove the pattern noise and reduce the error of later crop row detection. The modified Hough transform-based method effectively improved the peak detection accuracy by restricting the peak detection range with prior knowledge; Compare with traditional Hough transform-based methods, the averaged detection rate has increased from 30% to 67%, and the averaged CRDA has increased from 0.22 to 0.44. The modified green pixel accumulation-based method investigated the accumulation characteristics of the green pixels of the entire image, which effectively improved the angel detection accuracy; Compare with traditional green pixel accumulation-based method, the averaged detection rate has increased from 14% to 93%, and the average CRDA has increased from 0.12 to 0.69. The identification accuracy of the four methods from high to low were the modified green pixel accumulation-based method, the modified Hough transform-based method, the traditional Hough transform-based method, and the traditional green pixel accumulation-based method. 【Conclusion】This study improved the traditional crop row detection methods, which provided the technical support for the identification of wheat rows with high planting density and small row spacing.

Key words: wheat, planting rows, Hough transform-based method, green pixel accumulation-based method, UAV image