This study aimed to investigate the effects of differences in shooting and flight conditions for an unmanned aerial vehicle (UAV) on the processing method and estimated results of aerial images. Forest images were acquired under 80 different conditions, combining various aerial photography methods and flight conditions. We verified errors in values measured by the UAV and the measurement accuracy with respect to tree height and volume. Our results showed that aerial images could be processed under all the studied flight conditions. However, although tree height and crown were decipherable in the created 3D model in 64 conditions, they were undecipherable in 16. The standard deviation (SD) in crown area values for each target tree was 0.08 to 0.68 m². UAV measurements of tree height tended to be lower than the actual values, and the RMSE (root mean square error) was high (5.2 to 7.1 m) through all the 64 modeled conditions. With the estimated volume being lower than the actual volume, the RMSE volume measurements for each flight condition were from 0.31 to 0.4 m³. Therefore, irrespective of flight conditions for UAV measurements, accuracy was low with respect to the actual values.

This study examines the effects of differences in structure from motion (SfM) software on image processing of aerial images by unmanned aerial vehicles (UAV) and the resulting estimations of tree height and tree crown area. There were 20 flight conditions for the UAV aerial images, which were a combination of five conditions for flight altitude, two conditions for overlap, and two conditions for side overlap. Images were then processed using three SfM programs (Terra Mapper, PhotoScan, and Pix4Dmapper). The tree height and tree crown area were determined, and the SfM programs were compared based on the estimations. The number of densified point clouds for PhotoScan (160 × 10⁵ to 50 × 10⁵) was large compared to the two other two SfM programs. The estimated values of crown area and tree height by each SfM were compared via Bonferroni multiple comparisons (statistical significance level set at p < 0.05). The estimated values of canopy area showed statistically significant differences (p < 0.05) in 14 flight conditions for Terra Mapper and PhotoScan, 16 flight conditions for Terra Mapper and Pix4Dmapper, and 11 flight conditions for PhotoScan and Pix4Dmappers. In addition, the estimated values of tree height showed statistically significant differences (p < 0.05) in 15 flight conditions for Terra Mapper and PhotoScan, 19 flight conditions for Terra Mapper and Pix4Dmapper, and 20 flight conditions for PhotoScan and Pix4Dmapper. The statistically significant difference (p < 0.05) between the estimated value and measured value of each SfM was confirmed under 18 conditions for Terra Mapper, 20 conditions for PhotoScan, and 13 conditions for Pix4D. Moreover, the RMSE and rRMSE values of the estimated tree height were 5–6 m and 20–28%, respectively. Although the estimation accuracy of any SfM was low, the estimated tree height by Pix4D in many flight conditions had smaller RMSE values than the other software. As statistically significant differences were found between the SfMs in many flight conditions, we conclude that there were differences in the estimates of crown area and tree height depending on the SfM used. In addition, Pix4Dmapper is suitable for estimating forest information, such as tree height, and PhotoScan is suitable for detailed monitoring of disaster areas.

The Forest Stewardship Council (FSC) and the Sustainable Green Ecosystem Council (SGEC) are deployed as forest certification schemes in Japan. This study aimed to identify the reasons that enterprises choose the FSC or the SGEC scheme and the effects of certification. A questionnaire survey was conducted on 126 forestry enterprises with certification as of May 2014. The results of questionnaire tabulation found different reasons for choosing FSC (high reliability of the international certification system) or SGEC (examination costs and difficulty of acquisition, certification acquisition by neighboring enterprises in the region, and guidance and information from familiar people and enterprises). The results suggest that choosing FSC or SGEC depended on international or domestic emphasis, reliability, cost, and difficulty of acquisition. Both schemes reportedly improved management planning, environmental impact assessments, and monitoring, but increased timber value was not reported. Japanese consumers’ understanding of forest certification should be enhanced and attention to forest management certification in Japan should increase because the SGEC now offers international certification. If SGEC certification is easier to obtain than FSC certification, and FSC is relatively expensive, the SGEC forest area should continue to expand.

The purpose of this study was to compare the present condition of forest management in Asian countries using results of evaluations from Forest Stewardship Council (FSC) certification bodies. In recent years, the number of FSC-certified forests has increased in Asia. Our investigation examined certified forests in Asian countries, which, as of 2009, accounted for 2.39% of total global certified forest area (2,761,603 ha). Materials were taken from summary evaluations published by each FSC certification body on its respective website. The FSC uses 10 principles and 56 criteria in its evaluation. We investigated the items that the FSC certification bodies consider to be areas that require improvement. Of these principles and criteria, the following were cited by the certification bodies as RI (requiring improvement) in nearly all Asian countries: principle four, “community relations and worker's rights”; principle six, “environmental impacts”; principle seven, “management plan”; and principle eight, “monitoring and assessment”. In addition, there were differences corresponding to each country with respect to the other principles and criteria. Laos, Indonesia, and Malaysia in particular were found to have a number of problems. Thus, while there were differences in the principles that qualified as RI in each country, there were also common weak points that require improvement throughout the continent. Asian countries should be mindful of these deficiencies and take measures to improve them, in order to achieve sustainable forest management practices.