Abstract:

Objective: The application of Kalman filter in the resistograph drilling resistance sequence was studied. The resistograph stationary Kalman filter was derived,which provided a method and basis for estimating the age of standing trees. Method: Taking Larix principis-rupprechtii in Yangjuangou forest farm of Shanxi Province as the research object,323 sets of drilling resistance series obtained by resistograph drilling L. principis-rupprechtii in the same horizontal position and different directions were used as the research samples,and 104 stem discs were taken within 5 cm of the drilling position as reference samples. The general Kalman filter theory was applied in resistograph. By analyzing the characteristics of the filter,the parameters were simplified,and the stable Kalman filter was derived. The drilling resistance data obtained through the resistograph drilling into larch was used as input of stationary Kalman filter,and the output was the optimal estimation sequence based on the minimum mean square error as the best criterion,and the tree age was determined by the number of peaks and troughs of the optimal estimation sequence. The results estimated by the stationary Kalman filter algorithm,or auto-recognized by DECOM software were analyzed with the corresponding number of disc rings using paired data t-test. Result: The resistograph stationary Kalman filter reduced the number of initial parameters,the optimal estimation sequence of drilling resistance value only depended on parameter Rat. When the appropriate parameter Rat was selected according to their DBH size,the resistograph stationary Kalman filter applied in 323 groups of drilling resistance standing had better denoising effects,so that the algorithm estimating tree age was closed to the actual age. The relative error distribution of the algorithm was mostly between -10% and 10%,the minimum relative error was 0%,the maximum relative error was 25.69%,and the average relative error was 0.75%. Through paired data t-test,it was found that t-value was -0.468 16,indicating that there was no significant difference between the mean age estimated by the algorithm and the true mean age of trees. The relative error of the automatic analysis by DECOM software was large,mostly concentrated between -20% and -60%. The minimum relative error was -7.69%,the maximum relative error was -84.78%,and the average relative error was -40.49%. Through paired data t-test,it was found that t-value was 20.254,indicating that there was significant difference between the mean age estimated by DECOM software and the mean tree age of trees. Conclusion: The method of applying the resistograph stationary Kalman filter to the drilling resistance data sequence could accurately estimate the age of L. principis-rupprechtii,which might be better than the automatic analysis by DECOM software. This method is small invasive,fast and high accuracy,which provides an effective way for estimating the age of standing L. principis-rupprechtii.

Key words: Larix principis-rupprechtii, tree age, resistograph, drilling resistance data, the stationary Kalman filter, posterior estimation