Development and experiment of handheld digitalized and multi-functional forest measurement gun

Abstract: Forest mensuration is one of the basics in forestry science and the related fields. In this paper, a new handheld digitalized and multi-functional electronic forest measurement gun was designed and implemented to achieve digitalization, multi-function and precise mensuration in forest field inventory. Used to measure distance, angle of inclination and magnetic azimuth, the instrument was built upon such hardware as MEMS (Micro-Electro-Mechanical Systems) angle measurement sensor, and distance measurement laser sensor, MCU (Micro Controller Unit), flash memory, LED (Liquid Crystal Display), micro button, and USB (Universal Serial Bus). The instrument, based on the trigonometric principle, and operational software embedded, helped to achieve six functions in terms of individual tree height measurement, stand height measurement, stand density measurement, angle gauge, diameter and corresponding height at free position measurement, and basic measurement. To validate these six functions，a series of experiments were conducted respectively in 30 sample areas in Henan Province and 20 sample areas in Inner Mongolia, China. Data analysis and comparison demonstrated the following findings. In terms of tree height measurement, the measurements deviation of the electronic forest measurement gun and the total station was between 0.2%-1.6%, with an average accuracy of 99.39%. The relative error of angle gauge mounted on the electronic forest measurement gun and the lever-type angle gauge (Type: wi70448) was 4.75%, with the average accuracy of 95.25%. The relative error of stand mean height measured by electronic forest measurement gun and by average sample tree determination method was 5.03%, with the average accuracy of 94.97%. Compared with the conventional manual measurement approach, the relative error of numbers per unit area measurement function was 3.89%, with the average accuracy of 96.11%. When the forest measurement gun was used to measure diameter and corresponding height at free position, the relative error of diameter measurement between the forest measurement gun and tape was 4.42%. The relative error of corresponding height measurements between the electronic forest measurement gun and the total station was 1.25%, and the results correspond well with forest measurements. Regarding basic measurement functions, the average error of inclination measurement was 8′24″ and the average error of slope distance measurement was 5.56 mm relative to total station. The average error of azimuth measurement was 27′36″ relative to the angle scale. of all the functions, the accuracy of stand height was the lowest, 94.97%, while the accuracy of other functions was all above 95%. The results indicate that the instrument is able to meet the requirements of forestry field inventory and planning.