The Research And Practice Of Intelligent Measurement System For Tree DBH

The methods for accurately and efficiently measuring tree diameter at breast height(DBH)and other forest resource factors are always the basic needs for forestry investigators.However,the traditional forest inventory methods,which use calipers,girts and other tools,need to read and record data manually,which are not accurate,inefficient and prone to errors.The new forest inventory tools such as close range photogrammetry,lidar and total station,which are difficult to be widely promoted due to high cost of equipment,poor portability and weak environmental anti-interference ability.In this paper,the business of forestry investigation is deeply combined with sensor,embedded,computer and other technologies to develop an intelligent measurement system for DBH.The main research and work are as follows:(1)The exploration of DBH measurement methodBy studying the principles and characteristics of different types of sensors,three prototypes respectively based on rope sensor,capacitive grid sensor and angle sensor are designed.By comparing and analyzing the advantages and disadvantages of the three prototypes,it is concluded that the DBH measurement method based on angle sensor is more worthy of optimization and promotion.(2)The design of an embedded deviceThe embedded device is mainly composed of sensors,micro-computer,SD card,Bluetooth,display screen,buttons,power supply and other components.In this device,the DBH measurement method based on angle sensor from(1)is improved,and the tree position estimation using UWB technology and altimeter and tree coding using quick response code technique(QR)technology were integrated as auxiliary methods.So the device realizes the integrated measurement of DBH measurement,tree coding and position estimation.(3)The design of a data management softwareIn order to process the data of DBH,tree position and QR code,the data management software was designed and developed,which integrated data transmission,storage,management,statistics and analysis.And the software also realizes functions of automatic measurement for DBH,wireless data transmission,intelligent processing and personalized application.(4)The measurement testThis system was applied to measure ten square plots of diversified environments and various tree species to test its performance and accuracy of DBH and tree position.The DBH values had a bias of 1.89 mm(1.88% in relative terms)and a root mean square error(RMSE)of 5.38 mm(4.53%in relative terms).The tree positions were accurately estimated;the biases on the x-axis and the y-axis of the tree position were –8.55–14.88 cm and –12.07–24.49 cm,respectively,and the corresponding RMSEs were 12.94–33.96 cm and 17.78–28.43 cm.The average error between the estimated and reference distances was 30.06 cm,with a standard deviation of 13.53 cm.The device is cheap and friendly to use in addition to its high accuracy.The innovation of this study are as follows:(1)designing an innovative DBH measurement method using only two angle sensors;(2)estimating the position of trees using UWB technology and altimeter;(3)designing an intelligent measurement system which integrates tree DBH,tree coding,and tree position and has the functions of data automatic measurement,transmission, storage and analysis.