The Key Technology For Precision Measurement In Forest Surveying

It has an important significance and role to get the accurate surveying data on forest resource for the country to develop the forest policy and the medium-term planning, and also for forestry bureau to design the field surveying. For a long time, the forest resource surveying has some shortcomings, such as time-consuming, hard sledding, heavy workload, little accuracy and destruction of the forest, etc. So the paper made the forest resource surveying theory as the foundation, firstly, elaborated the latest methods of surveying, including polygonal plot method and nondestructive standing tree volume measurement, and then studied the instruments requirement of nondestructive standing volume measurement, measurement accuracy, compilation of unitary volume table and duality volume table and their precision analysis, finally analyzed the layout principle of the polygonal plot, precision and conditions. The paper aimed to provide a theoretical basis for the national forest resource survey by using the easiest way to solve the complex survey questions. The main research contents can be summarized as follows:1The principle and accuracy analysis of nondestructive precision auto-measurement in standing tree volumeThe principle and technical methods of nondestructive standing tree volume can be explained with analytic geometry, mathematical analysis and probability statistics and other mathematical principles. Choosing a pole, known the true value, as the object of study, to clarify the standing tree volume measurement with instrument of the electronic theodolite, and studying the impact of the external factor, including different areas, different observation distance, different observation orientation, multi-faceted average, different observers and different electronic theodolite on this method’s accuracy. After analysis, we get the factors affecting the accuracy and bring forward the best observing programs. On account of1003trees of ten common species, the trees volume are measured, like birch, dahurian birch, korean pine, larch, aspen, acer mono maxim, chinese pine, elm, oak, scotch pine planted in Wangyedian forest farm, located in Harqin Banner, Chifeng city, Inner Mongolia. In which, selecting representative87trees (four species, five diameter classes and four kinds of slope and aspect), and letting different observers observe the trees in different direction and distance to get the data to put forward the best observation azimuth and distance range.2The establishment of unitary volume model and duality volume model and their precision analysisBased on the proportion of ten species in the Wangyedian forest farm, the numbers of each diameter class were calculated and the1003trees volume of ten common species were measured in different diameter classes, from6cm to60cm, by using nondestructive auto-measurement technology, and the80%amount of trees volume data were selected to build the model and elect the optimal unitary and duality volume models through the analysis of the error factors of correlation coefficients and mean square deviation. The other20%amount data were combined with the data of trees felled before to get the tree height and the average volume, including ten species and seven common diameter classes (16cm,18cm,20cm,22cm,24cm,26cm and28cm),40trees of each class, while the data saved of acer mono maxim were less than40trees, so we change to10trees, and all the trees amount to2590trees. Though testing with the volume table to verify the accuracy of the model, the results showed that the average accuracy of unitary volume model and duality volume model all reached more than95%, and met the precision of volume table. Duality volume model’s deviation rate in ten species was less than unitary volume model which showed that the stability of duality volume model was better than unitary volume model.3The forest resource surveying and monitoring research of polygonal plotsThe principles and technical methods of forest resource surveying of polygonal plots can be interpreted with space analytic geometry, sampling statistics, the total station electromagnetic ranging and biological spatial distribution and ecology principle. Firstly, selecting the representative four forest lands, including loose plantation, dense plantation, loose natural forest and dense natural forest, in which the rectangular plots,20m*30m or30m*30m were built, with total station lofting techniques. Secondly, measuring each tree’s height, DBH, volume and coordinate with total station, electronic theodolite and DBH scale to get the average stand height, stand density, the average DBH, and the sum of volume, namely, stand volume of the four rectangular plots, and these stand characteristics were made as the true values. Thirdly, comparing the average stand height, stand density, the average DBH, and the stand volume of5-10polygonal plots built in the four forest lands with the true values to discriminate accuracy. At last, accumulating all the polygonal plots in each rectangular plot to get the average stand characteristics factors and comparing with the true values to discriminate accuracy and determine the suitable polygonal plots numbers in different forest farm.4Combination with polygonal plots method and forest map to calculate the stand volumeUsing the mechanical sampling method to lay out203polygonal plots location in the forest map with recording every location’s coordinate, and laying out the polygonal plots in the forest land under leading by staff with the help of Beidou satellite navigation and positioning system. Firstly, recording the coordinate of each tree marked with paint in the plots, including height, DBH with the help of DBH scale, Beidou satellite navigation and positioning system and total station, secondly, inputting all these data into specially prepared polygon program to calculate the average stand height, stand density and stand volume and other stand characteristics factors. At last, gathering every sublot’s area in the forest map and calculate each sublot’s volume with the principle of proximity, and total forest stand volume of the Wangyedian forest farm is3098005.056m3.5Combination with polygonal plots method and resources satellite No.3images to calculate the forest stand volumeThe203polygonal plots location were selected as the ground-based observations by the resources satellite No.3images to inverse the model for volume accumulation, through estimating by the model. The accuracy of the analysis show that:coniferous and broadleaf forest model forecast accuracy reached 82.51%,80.12%, respectively.The innovation of the paper can be summarized as follows:1The new technology of the electronic theodolite measuring the standing tree was proposed and applied with non-felled in the Wangyedian forest farm to establish the unitary volume model and duality volume model.2The polygon method was combined with standing volume method to calculate the forest stand volume.