基于智能手机与机器视觉技术的立木胸径测量方法

Tree DBH measurement method based on smartphone and machine vision technology

针对现有森林资源调查中立木胸径测量工作劳动强度大、效率低,先进设备操作复杂、成本高等问题,结合相机标定、三维重建、机器视觉和近景摄影测量等技术,探索基于智能手机与机器视觉技术的立木胸径测量方法。通过智能手机获取待测立木的图像信息,运用Lab颜色空间模型(Lab color model)和3×3算子对图像进行卷积运算,得到立木图像的视觉显著图;结合HSV颜色模型(色调H,饱和度S,明度V)中的H分量增强图像中立木树干部分的颜色对比度,通过图像分割算法识别并获取自然环境下的目标立木轮廓区域;通过一种改进的带有非线性畸变项的相机标定模型标定智能手机的相机内、外参数,并借助相机参数和二维图像信息进行三维世界坐标重建,从而实现树干1.3 m处胸径的测量。经验证,一定距离内胸径测量结果的相对误差小于2.50%。该方法测量精度较高,符合森林资源调查对胸径测量的精度要求,可应用于森林资源调查。

Aiming at the problems of high labor intensity and low efficiency,complicated operation and high cost of advanced equipment in the measurement of DBH in existing traditional forest resources,and proposing a method for measuring diameter at breast height(DBH)based on smartphone and machine vision technology,and combining with camera calibration,3D reconstruction,machine vision,close-range photogrammetry,and other technologies.First,The original image is obtained by smartphone,and the visual saliency map of the preprocessed image is processing by using the lab color space model and 3×3 operator to convolving with image.Combining with the H component of the HSV(Hue,Saturation,Value)color model to enhance the color contrast part of the tree trunk in the image.The image segmentation algorithm is used to identify and obtain the target tree’s contour in a natural environment.Then,an improved camera calibration model with nonlinear distortion terms is used to calibrate the camera’s internal and external parameters.Finally,achieving reconstruction of a 3D world with camera parameters and two-dimensional image information is carried out to measure DBH at a height of 1.3 m.Experimental results indicated that within a certain range,the relative error of the DBH measurements was lower than 2.50%.This method has a high measurement accuracy,meeting the accuracy requirement of DBH measurement in forest resources investigation and could be applied in forestry resource surveys.