A Comparative Evaluation of Unmanned Aerial Vehicles (UAVs) for Forest Survey
Aor Pranchai, Kampanart Sirirueang, and Naraporn Zonklin
Small unmanned aerial vehicles (UAVs), or drones, are being used increasingly in mapping, monitoring, and inventorying forests. However, there is a lack of guidelines which can help forest managers in selecting a suitable UAV, cameras, and survey settings for a specific forest area. The objective of this study was to develop an overview by comparing the circumstances under which multicopter and fixed-wing UAVs can be used in forest surveys. The general relationships of ground sampling distance, image overlap, flight altitude, and speed, as well as the camera system were established and described. Based on these relations, the UAV systems were compared for their applicability and efficiency in surveying different forest areas. The comparison of multicopter and fixed-wing UAV systems showed that surveys of large forest areas at a ground sampling distance (GSD) of more than 5 cm should be conducted using fixed-wing UAV to shorten flight times and improve survey efficiency. In contrast, surveys of tree seedlings would require a multicopter, whose low flight speed could ensure high image overlaps at a high ground resolution. Thus, the selection of a UAV system is mainly dictated by the required GSD and survey area.