Improvement of pressler method for predicting tree height with terrestrial laser scanning

An important problem of the forest inventory using the terrestrial laser scanning (TLS) is the undermeasured tree height. To resolve this problem, we improved Pressler method, which is originally proposed for estimating stem volume, as follows: the diameter at breast height is reduced by a certain ratio, and then the height above ground level at the position of the reduced diameter is defined as the critical height. The relationship between critical height and tree height is also formulated in advance using data on stem form of felling trees. Then, inserting the critical height measured with TLS enables us to estimate the tree height. Using felling tree data of four coniferous species (Japanese cedar, Japanese cypress, Japanese larch and Jack pine), the relationship between critical height and tree height was analyzed, and the applicability of the improved method was evaluated. The results demonstrated that the underestimation of the tree height can be reduced if the critical height can be measured with TLS.