Comparative Study On Comprehensive Technologies Of Tree Height Measurement

Tree height is one of the most important measurement factors in the forest survey,which is a significant basis for the estimation of site quality,forest growth and story division.The tree height can not only reflect the productivity of the forest land,but also can determine the tree volume and volume increment percent.Meanwhile,tree height is one of the main factors of volume table compilation and forest volume determination as well,the must in forest survey.The conventional tree height measurement of extensive forest resources survey and monitoring uses the visual estimation or simple instrument measurement with low precision,failing to meet the requirement of precision forestry and digital forestry.It is necessary to do harmless measurement to the single tree or forest nowadays,when we have less and less forest resources.In this study,the high precision instruments like the electronic theodolite and total station instrument were used in the forest survey,combined with the need and development of the precision forestry and digital forestry.Five types of tree height measurement methods were compared and analyzed in the basic principle,function and characteristics.In addition,different measurement instruments and methods concerning the hypsometer,compass,electronic theodolite and total station instrument under the condition of various terrain and envirionment.In the testing field of Jiufeng National Forest Park,30 trees were selected randomly and the height of each tree was measured for 30 times.According to the discriminant analysis,induction of the tree height data,there came the regular conclusion:due to the restriction of the terrain,slope and forest intensity,it is hard to get the horizontal distance measurement data or not easy to select the observation sites,which leads to the hardship in the direct measurement of the target trees. Therefore,3D angle measurement intersection and the total station twice in one plumb side measurement were proposed for tree height measurement.The study provides the development of the precision forestry technology system with the new technical support,which meets the real time mechanism and lossless characteristics in the forest resources survey.In addition,the tree height measurement area with bad condition or the area hard to reach has been realized.