A laser scanning system for estimating wind velocity reduction through tree windbreaks

The performance of trees as windbreaks is principally determined by their geometric characteristics. This paper reports the development of a laser scanning system to measure tree geometric characteristics on-the-go and its use to estimate percent wind velocity reduction in a windbreak. The laser scanning system was built by mounting a laser sensor, a global positioning system (GPS) receiver, and a notebook computer on a test vehicle. A windbreak was established by arranging a set of large potted trees in a pattern that provided two porosities for wind velocity measurements (windbreaks I and II). Winds generated by a blower at low and high wind velocities were directed at the centers of the tree windbreaks. Wind velocities were measured using a vane anemometer in four areas of the windbreaks, both on the windward and leeward sides. Percent wind velocity reductions between the windward and leeward sides were calculated. The laser scanning system measured the tree canopy geometric characteristics in the same areas where the wind velocities were collected. The linear correlations between the tree canopy geometric characteristics and the percent wind velocity reductions were analyzed. In tree windbreak I. the highest correlation coefficient (r) of 0.97 (root mean square deviation - RMSD = 3.61%) and 0.96 (RMSD = 3.29%) were obtained at the low (<16 in s(-1)) and high (<20 m s(-1)) wind velocity conditions, respectively. On the other hand, in tree windbreak II, the highest r values of 0.93 (RMSD = 4.59%) and 0.98 (RMSD = 2.26%) were estimated at the low (<12 m s(-1)) and high (<18 m s(-1)) wind velocity conditions, respectively. (C) 2010 Elsevier B.V. All rights reserved.