The Extraction Of Tree Parameter And Modeling Analysis Based On Terrestrial Laser Scan

The point cloud data extracted through Terrestrial Laser Scan(TLS)can be used for nondestructive forest measurement,especially for the upper diameter of tree trunk,which improve the precision of tree parameter extraction.With this technology,it can provide a new way for modeling tree from three-dimensional,conducting increment study and monitoring the change of forest resource.Particularly,density impact of tree factors for poplar plantation forest based on the TLS data help for selecting the best planting density.It is possible to select the best scheme for plantation cultivation,and to realize sustainable forest managementfor useing forest resources in a reasonable wayin order to alleviate the shortage of forest resources.In this research,K-means clustering method was used for extracting tree trunk through point cloud data.The diameter and height parameters of the tree were extracted automatically through the cross section of laser data,which provided the basic data set from standing trees on different planting density.Then,this research analyzed the forest measuration factors and the turning point of taper equation,established a set of stand level prediction model based on the TLS point cloud data.Through laser scanning and above research methods,the tree measurationt factors of four different planting densities(from high to low planting spacing:3 m×8 m,5 m×5 m,4.5m×8m,6m×6m)and three clones(Nanlin-95 poplar,Nanlin-797 poplar,Nanlin-895 poplar)were studied,the main findings and resultsare as follows:(1)The precision of automatic extraction of tree parameters based on TLS data ishigher.The precision of automatic diameter extraction based on least square method is up to 96%,which is better than that of Hough Transform method,and the precision of tree height extraction is 95.33%.The factors that have significant effects on the DBH,tree height,and individual volume are planting densities,planting spacing configuration,clones,the interaction of different clones and different planting densities.Among them,the affection form the lowest density 6 m×6 m with square planting spacing configuration was significantly larger than those densities stands.The average values were 24.96cm、24.5m、0.4883 m~3.The tree trunk for high-density is straighter and low-density is relative taper.(2)Based on the TLS data,the trunk shape model were built through the standing tree parameter data which were automatically extracted for different planting densities.The best relation model for form factor and form quotient of breast height is the model 5.1.1-4,for high-density,low-density,the whole stand and the better taper equation model of different density is model 5.1.2-3 that is piece wise taper equation.The result of fitting the optimum taper for low-density stand was better than that of high-density,the parameters withinhigh-density plots and withinlow-density plots are very close.The relative height of upper and lower inflection point in high-density is 0.94,0.23 respectively,and the relative height of upper and lower inflection point in low-density is 0.81,0.09,respectively,the results shows that the trunk with high-density is straighter,and the trunk with low-density is taper.At high-density,the arrangement of planting spacing(5 m×5 m)promoted the growth of trunk shape,but there was no significant difference in trunk shape of different planting spacing at low-density.(3)The standard volume tables and merchantable volume tables for different density stands based on the optimum taper equation equations were established through TLS data,the highest estimated volume per plant was from low-denstity planting space 6m×6m,up to 0.5819m~3.The highest general outturn percentage of small diameter per plant was from high-denstity planting space 3m×8m,up to18.80%,the highest general outturn percentage of middle diameter per plant was from low-denstity planting space 6m×6m,up to 40.87%.Those tables were used to analyze the difference of the total accumulation and the total timber output of four stands with different planting density per unit area.The results shows that the total accumulation per unit area of square planting space for high and low density were all above 160 m~3/hm~2,the highest total timber output of small diameter timber per unit was from high-density planting space 5 m×5 m,up to 25.3594 m~3/hm~2.The highest total timber output of middle diameter timber per unit area was from low-denstity planting space 6m×6m,up to 65.4676 m~3/hm~2.The results showed that under different timber assortment with higher total accumulation and the total timber output,planting spacing of square was obviously superior to rectangular plants.