Validation of Mobile Laser Scanning for Understory Tree Characterization in Urban Forest

This study was dedicated to validating mobile laser scanning (MLS) for understory tree characterization, which now is still an open issue of interest in the fields of forest inventory and remote sensing. The program of validation was divided into three steps aiming at its three premise questions, respectively: 1) Can MLS record echoes with precise coordinates in the scenario of forest overstory shading satellite wireless positioning signals? 2) Can MLS samplings subject to spatial distribution inconsistency show the basic structures of understory trees? and 3) Can MLS data, further, present the local details of understory tree structures? The examinations were carried out based on the related typical feature variables, i.e, 1) overstory tree stem positioning accuracy as a substitute and 2) understory tree height and crown width and the newly proposed measure of object detail characterization, i.e, 3) primary nearest point distance (PNPD). The results proved to be positive. Overall, although the discussions suggested that MLS has its shortages, e.g, its cover still restricted by tree obscuration, this endeavor has primarily validated MLS for understory tree characterization in urban forest.