【摘要】 热红外影像较难直接提取作物冠层区域,因而无法获得较精准的作物冠层温度。本文以拔节期的玉米为研究对象,利用六旋翼无人机搭载热红外成像仪和大疆精灵四Pro无人机,获得热红外影像及正射影像。基于高分辨率正射影像,采用改进的Canny边缘检测算子、支持向量机(Support vector machine,SVM)和小波变换3种方法提取玉米冠层区域,将提取结果进行二值化处理后,在热红外影像中以此生成掩膜并提取玉米冠层温度。应用提取的矢量面分析提取效果并对3种提取算法的精度进行评价。实验结果表明,改进的Canny边缘检测算子提取效果最优、SVM算法次之、小波变换最差,提取精度分别为87. 3%、74. 5%、68. 2%。同时,将手持测温仪测得的玉米冠层温度与提取的冠层温度进行误差分析,结果表明,基于改进的Canny边缘检测算子提取的玉米冠层温度与地面实测值相关性最高,决定系数R~2=0. 929 5,SVM算法决定系数R~2=0. 895 7,小波变换决定系数R2=0. 876 0。改进的Canny边缘检测算子能够更好地提取玉米冠层区域,获取更加精确的玉米冠层温度,从而能够更有效地监测玉米生理状况,进行旱情预测,制定合理的灌溉、施肥措施以提高玉米产量。更多还原

【Abstract】 For the low resolution of thermal infrared image,the crop canopy area can not be accurately extracted,and accurate canopy temperature can not be obtained. Maize in the jointing stage was taken as research object,and the thermal infrared image and orthophoto were obtained by using the UAV equipped with thermal infrared imager and the Dajiang Elf Pro UAV. Based on high-resolution orthophotos,the improved Canny edge detection operator,support vector machine( SVM) and wavelet transform were used to extract the maize canopy region,and the classification results were binarized in thermal infrared imaging. The maize canopy temperature was extracted by using the mask generated by the binarization result. The extracted vector surface analysis extraction effect was applied and the accuracy of the three extraction algorithms was evaluated. The experimental results showed that the effects of the three methods from strong to weak were as follows: improved Canny edge detection operator,SVM and wavelet transform; the extraction accuracy was 87. 3%,74. 5% and 68. 2%,respectively. At the same time,the error analysis of the maize canopy temperature measured by the hand-held thermometer and the extracted canopy temperature was performed. The experimental results showed that the correlation between the canopy temperature extracted by the three algorithms and the measured temperature of the ground from strong to weak was as follows: 0. 929 5,0. 895 7 and 0. 876 0. The improved Canny edge detection operator can better extract the maize canopy area and obtain more accurate maize canopy temperature,so as to more effectively monitor the physiological status of maize,predict drought,and formulate reasonable irrigation and fertilization measures to increase maize yield.更多还原