UWB定位摄影测树仪设计与试验

Design and test of photographic dendrometer based on Ultra Wide Band(UWB)positioning

为了实现森林样地高效、精准测定,该研究研制了一种具有实时定位功能和林分摄影测量功能的超宽带(Ultra Wide Band,UWB)定位摄影测树仪,该仪器主要由姿态传感器、UWB定位模块、CCD镜头和固定杆组成,以UWB定位技术和摄影测量理论为基础,结合到达时间差(Time Difference of Arrival,TDOA)定位算法、三边定位算法、运动恢复结构(Structure From Motion,SFM)点云匹配算法实现摄影测树仪的林下精准定位、影像获取以及林木坐标测量、胸径测量功能。为了验证仪器的林分参数提取准确性,选择4种不同林种的人工林进行试验。根据摄影测量影像特征点的匹配特点,设计“环绕拍摄”样地观测方法,利用Pix4D软件对拍摄的影像和点位坐标进行三维点云构建,利用LiDAR360对重建后的三维点云进行去噪处理、胸径和立木位置提取。结果表明,所设计的仪器能够快速获取样地影像和影像坐标信息,胸径测量值的偏差为-0.04~0.42 cm,均方根误差为0.26~0.51 cm;立木位置测量值偏差为-0.16~0.27 cm,均方根误差为0.23~0.34 m。胸径测量精度能够满足森林资源调查的精度要求,可进一步推广应用于森林资源调查。

Estimation of trees position and Diameter at Breast Height(DBH)is an important part of forest resources inventory.This study aimed to design a multi-functional,high-precision,real-time positioning tree-measuring device that integrates plot setting,DBH measurement,and tree position measurement based on the Ultra Wide Band(UWB)positioning principle,sensor technology,image processing technology,trigonometric functions and tree surveying theories.The main hardwares component of the equipment included CCD(Charge Coupled Device)image acquisition module,antenna,three-axis gyroscope module,three-axis accelerometer module and console module,the auxiliary components included fixed cloud platform and lithium battery.The software was developed by a modular structure compiled in android windows development environment based on the C++language.According to the matching characteristics of the photogrammetric image feature points,the"surround shooting"sample plot observation method was proposed.The pix4D commercial software was used to established the three-dimensional point cloud model of the trees,and the LiDAR360 software was used to denoise the reconstructed 3D point cloud,extract the DBH and the position of the trees.In order to verify the accuracy of stand parameter extraction,the device was tested in four plots,that was Salix matsudana Koidz,Pinus tabuliformis Carr,Quercus mongolica and Koelreuteria Paniculat respectively.The results showed that the designed photographic dendrometer could be used to obtain the image of the trees and coordinate information in image quickly,the deviation and RMSE(Root Mean Squared Error)of the DBH were-0.04-0.42 cm and 0.26-0.51 cm,and that of the position were-0.16-0.27 m and 0.23-0.34 m,respectively,the measuring precision conformed to the requirements of forestry investigation.The study can provide a reference for the forest survey.