Measure method of tree height and volume using total station under canopy cover condition

Abstract: The height and volume of trees is one of the most significant factors in a forest survey, it has important significance for the investigation of forest resources and forestry scientific research. In order to solving the problem that we cannot confirm a single tree's volume exactly, which is caused by the inability to determine the tree height, when a part of the tree crown was in the shade, this paper utilized a different method for setting-out the tree height using a total station to measure the diameter at breast height (DBH), the diameter of the maximum observation point and the middle point's diameter of those two points, and the corresponding distance to the ground in the field investigation. This test observed 334 trees including 188 larch (Larix gmelinii) trees and 146 white birch (Betula platyphylla Suk), using a similar triangle method, single tree growth empirical equation method and Kunze, M. stem curve method to estimate the tree height and volume of every standing trees by constructing mathematical model. At the same time, there were four hypotheses of the highest observation points in the test, those four stations respectively being in 1/3H, 1/2H, 2/3H, and 9/10H. The three different methods above was used to calculate the tree height and its volume in this four different maximum observation station, and analyzing the precision of every situation. Respectively, the method of similar triangles, simple growth experience equation method and Kunze, M. stem curve method were used to build mathematical model, and through the model combined with tree growth and stem form theory to estimate the tree height and volume. This method only needs to measure a few stem diameter value and the corresponding height, combined with the tree growth equation and stem curve equation can estimate the height. Compared to the conventional method, the tree height precision using the new method was greatly improved. And using remote sensing technology of image reconstructed images of three-dimensional model for tree height method can simplify huge image data calculation process, and improve the efficiency of tree height measurement. The results show that the estimated height and volume values are more accurate with the increase of the maximum observation points. In those three methods, the accuracy can reach to 70%-80% with the tree growth empirical equation and 70%-90% with the Kunze M. stem curve method. Thus, the new method is satisfactory to measure a single tree's volume when it is in the shadow, and it has a very important significance for the actual production.