Development and Testing of a New UWB Positioning Measurement Tool to Assist in Forest Surveys

Abstract

Forest resource inventory is a significant part of the sustainable management of forest ecosystems. Finding methods to accurately estimate the diameter at breast height (DBH), tree height and tree position is a significant part of forest resource inventory. The traditional methods of forest resource inventory are expensive, difficult, laborious and time-consuming; the existing systems are not convenient to carry, resulting in low working efficiency. In addition, it is usually necessary to rely on a forest compass, DBH taper and RTK or handheld GPS to set up the plot. These instruments each have a single function and cannot achieve accurate positioning under the forest canopy. Therefore, it is necessary to update the existing equipment and technology. This study aimed to design. a multi-functional, high-precision, real-time. positioning intelligent tree-measuring instrument that integrates plot the set-up, DBH measurement, tree height measurement and tree position measurement. The instrument is based on the ultra-wideband positioning principle, sensor technology, image processing technology, trigonometric functions, tree surveying and other related theories and realizes the functions of plot set-up, tree position measurement, DBH measurement, tree height measurement and other functions. The device was tested in four square plots. The results showed that the root mean squared. error (RMSE). of the tree position estimates ranged from 0.07 m to 0.16 m, while the relative root mean squared error (rRMSE) of the DBH estimates of individual trees ranged from 3.01 to 6.43%, which is acceptable for practical applications in traditional forest inventory. The rRMSE of the tree height estimates ranged from 3.47 to 5.21%. Furthermore, the cost of this instrument is only about one-third that of traditional forestry survey tools, while the work efficiency is three times that of the traditional measurement methods. Overall, the results confirmed that the tree measuring instrument is a practical tool for obtaining. accurate measurements of the tree position, DBH and tree height for forest inventories.

The Development of a Set of Novel Low Cost and Data Processing-Free Measuring Instruments for Tree Diameter at Breast Height and Tree Position

“…Fan et al [1] obtained a +0.33 cm bias and a 1.26 cm RMSE for tree DBH measurements using a mobile phone with a TOF camera and SLAM technology. Zhao et al [23] used a ground photogrammetry method to estimate tree DBH, and reported a rRMSE of the DBH estimates of individual trees that ranged from 3.01 to 6.43%. Liang et al [56] estimated tree DBH using a multi-single-scan TLS method in forest inventories, and reported a RMSE range from 0.90 to 1.90 cm.…”

“…Tang et al [58] used a small-footprint mobile LiDAR to scan a study area, and reported a positioning accuracy better than 0.32 m in two different areas, with expensive and heavy hardware. Zhao et al [23] also used UWB technology to estimate tree positions, and reported a RMSE range from 0.07 m to 0.16 m. However, their UWB positioning method required calibration of the four corners of the plot, and each corner was placed with a UWB module. Thus, the method was complex and time-consuming.…”

“…During the last three decades, many forest surveying methods have been proposed [1,7,[12][13][14]. From the traditional forest inventory to modern solutions and practices, new measurement methods using electronic tools, wireless sensors, and the Internet of Things (IoT) are gradually being applied [11,[20][21][22][23]. These methods can be divided into two categories: contact methods and non-contact methods [24][25][26].…”

“…Therefore, this technology is particularly suitable for measuring distance and positions in forests. Zhao et al [23] developed a new UWB positioning measurement tool to estimate tree positions; however, similar to other indoor UWB positioning methods, they all required setting up at least four UWB modules for anchors at four corners and one UWB module as a tag. Additionally, in order to calculate the position of the UWB tag, surveyors must obtain the three-dimensional (3D) coordinate positions of the UWB anchors before each sample plot measurement.…”