Laser scanning based three dimensional measurement of vegetation canopy structure

Three-dimensional vegetation canopy structure is the critical original data source for the evaluation of radiation transfer modeling, remote sensing products validation and many other remote sensing applications. Although a number of three-dimensional measurement techniques have been already used in industrial measurement, few of them can be directly applied to vegetation canopy structure measurement because of the insufficient ability of non-contact and field measurement, as well as the possibility of matching with other information like vegetation spectra. In this paper, a non-contact laser scanning based three-dimensional measurement system is proposed to acquire the structure of the vegetation canopy, which is based on the flying point scanning triangulation. It gives a way of obtaining dense canopy structure data in-situ without neither contacting nor sticking the targets on the vegetation. The system principle, modeling and novel calibration approach, which directly calibrates the equation of the incident laser beam and other key techniques related to the system implementation are presented and discussed in detail. The system's measurement ability is demonstrated by acquiring different shaped leaves. The scanning point separation and the accuracy of three-dimensional points are 3-5 mm and 1 mm respectively. The points can then be used to calculate the geometric descriptive parameters of the canopy including plant area, leaf overlap, leaf area index, and gap fraction. It can also be used to establish highly detailed three-dimensional digital model of the vegetation canopy.