A precise method to measure the trunk diameter of standing tree using total station

Considering that the trunk diameter is an important indicator in the forest resources survey, a new precise method based on Tie Distance principle was introduced to measure the trunk diameter of the standing tree . The theoretical accuracy of this method was validated by using instrument of South Total Station NTS-3401 with non-prism, and the actual accuracy was analyzed combining with real measured values. The results showed that the mean square error of theoretical accuracy with the South Total Station NTS-3401 was less than 0.4 mm. In order to verify the accuracy with South Total Station NTS-3401, the mean value of measured results for three time with DBH (diameter at breast height)ruler was used as the real data, and the real error was within 1 mm, which meets the requirement of forestry measurement, that nearest to 1 mm. Therefore the method of the total station satisfies the accuracy requirement of millimeter level in measuring the diameter of standing trees in forestry measurement, and could solve the difficulty of non-contact measuring the diameter of trunk at the part higher than over 2 m