摘要
以北京市杨树立木材积实测数据作为检核真值,按误差传播定律对电子经纬仪测树误差进行分析,并依据我国电子经纬仪精度划分的Ⅰ（DJ1）、Ⅱ（DJ2）、Ⅲ（DJ6）和Ⅳ（DJ15）4个等级,计算该方法测量树高和材积的误差和2倍中误差的极限误差,分析不同精度电子经纬仪测树的差异性和适应性。结果表明：由于误差的传播和累积,同一精度电子经纬仪测量材积的误差大于树高。同一精度电子经纬仪测量不同规格样木时,误差会随着树木大小的变化而略有差异。随着电子经纬仪测角标准偏差的变大,测树的误差也会变大。电子经纬仪标准偏差为±0.5″时,测量树高和材积的中误差分别为±6.550 0×10^-2m和±1.474×10^-3m^3,相对误差分别为0.44%和0.73%。电子经纬仪标准偏差为±15.0″时,测量树高和材积的中误差分别为±8.927 5×10^-2m和±4.385×10^-3m3,相对误差分别为0.60%和2.14%。说明我国现有的Ⅰ-Ⅳ级电子经纬仪测树结果均符合相对误差不超过3%-5%的精度要求,可以满足不同林业调查工作的需要。
In traditional forestry works, the compilation of volume tables by cutting down trees and using analytic timber volume estimations is faced of problems such as large destruction, high costs and low efficiency. Therefore, an estimation method was proposed. First, diameter at breast height and ground diameter were manually measured. Then, the horizontal angles and zenith distances at corresponding trunk positions of live standing trees were measured by using the approximate division of analytic timber based on an electronic theodolite. Finally, the timber volume was estimated by simulating mean sectional division volume as per summation of conical frustum. The measured data of standing timber volumes from poplar in Beijing were used as true data for examination. The errors of timber measurement from electronic theodolites were theoretically analyzed according to error propagation laws. Based on the four grades of electronic theodolite precision classification in China： Ⅰ （ DJI ）, Ⅱ （ DJ2 ）, Ⅲ （ DJ6 ） and Ⅳ （DJ15）, the errors and the limit errors of root mean square error （RMSE） during measurements of tree height and timber volume were computed. Moreover the differences and applicability of electronic theodolites with different precision levels were analyzed. The results showed that because of error propagation and accumulation, the errors of timber volumes measured by electronic theodolites with the same precision were larger than the errors of tree height. When timbers with different sizes were measured by electronic theodolites of the same precision level, the errors slightly changed along with the size of timbers. With the increased standard deviation in angle measurements by electronic theodolites, the errors in forest measurement also increased. When the standard deviation of electronic theodolites was ±0.5＂, the RMSEs in measurements of tree height and timber volume were ± 6. 550 0× 10^-2 m and ± 1. 474 × 10^-3 m^3, respectively, while the relative errors were 0.44% and 0.73% , respectively. When the standard deviation of electronic theodolites was ±15.0＂, the RMSEs in measurements of tree height and timber volume were ±8. 927 5 × 10^-2 m and ± 4. 385× 10^-3 m^3, respectively, while the relative errors were 0.60% and 2.14%, respectively. Therefore, the existing Ⅰ - Ⅳ electronic theodolites applied into tree measurements all conform to the precision requirement that relative errors do not exceed 3% -5% , and satisfy the requirements of different forestry works.
出处
《农业机械学报》
EI
CAS
CSCD
北大核心
2015年第1期292-298,共7页
Transactions of the Chinese Society for Agricultural Machinery
基金
国家自然科学基金资助项目(41371001)
关键词
电子经纬仪
立木材积
树高
误差传播定律
Electronic theodolite Standing tree volume Tree height Laws of error propagation
