# BVLOS Unmanned Aircraft Operations in Forest Environments  
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1 Schon, 49 Sala Street, Private Bag 3020, Rotorua 3046, New Zealand1 Sch  
the Southern Hemisphere, which covers approximately 180,000 ha [1]. Natural forests can be an order of magnitude larger, again, with the world's largest forest, the boreal Forest, covering 1.2 billion ha, or approximately 9% of the land area of Earth [2]. Plantation forests are typically broken up into smaller stands of 10 to 100 ha for management purposes, making them somewhat more accessible to UAVs, so this would be representative of the size of a typical UAV operation for forestry. UAV operations in forested areas, however, are not confined to smaller areas, with some studies using UAVs for wall-to-wall captures over larger areas of 200-340 ha [3; 4]. The trees themselves also present an obstruction to line of sight (VLOS) and require frequent movements of pilots or the use of expensive equipment, such as mobile elevating work platforms (MEWP), in order to maintain VLOS [5]. The ability to fly BVLOS, in such instances, would make operations far easier for the operator. However, there are some significant regulatory and operational barriers that would need to be overcome for such operations to begin. There are also clear applications of unmanned aircraft within forest environments, such as wildfire monitoring and suppression, carrying out inventory and health assessments of forestry plantations, conducting wildlife research, flora and fauna conservation efforts, dropping seed capsules to help with reforestation, spraying of herbicides to kill invasive plant species, and dropping poisons and traps for pest control, among others [6; 7; 8; 9; 10; 11; 12; 13; 14; 15; 16]. One of the common characteristics to all of these applications is that the ability to cover large areas is desirable. However, if conducting VLOS operations, the operating area is limited by human vision. There are different estimates of what distance a human could visually detect unmanned aircraft from given variations in meteorological visibility, the size of unmanned aircraft, and the location of the person detecting the aircraft (e.g., on the ground vs. on board another aircraft) [17; 18; 19]. Operational experience from the authors suggests that between 500 m and 2 km VLOS would be usual for most craft sizes in visual meteorological conditions. However, due to the variations that might be expected based upon aircraft size, colour, use of lighting, and meteorological conditions, we do not argue a precise value and, rather, present Table 1 to show how VLOS operations can significantly reduce the size of operating areas. While Table 1 shows the effect of VLOS on possible operating areas, one further consideration to take into account is that all forest areas have a common visual obstruction: the presence of trees. Figure 1 visually depicts how moving a very small distance over tree cover can result in complete loss of VLOS when flying a craft in a simple scenario over flat terrain. Due to the difficulties associated with maintaining VLOS, operations often take place from clearings, high vantage points, or the pilot may use a MEWP. If none of these are available, the pilot may need to frequently relocate themselves to maintain VLOS or employ visual observers to conduct what is called an Extended Visual Line of Sight (EVLOS) operation, where the pilot loses VLOS, but a visual observer maintains VLOS and is in direct communication with the pilot [20]. Aside from affecting the ability of the pilot to maintain VLOS of the aircraft, trees can also limit the pilot's ability to scan the surrounding airspace and mitigate the potential of an airborne collision. Although many UAV users, in commercial forestry, operate at or below 400 ft, due to regulatory considerations, numerous operations in forest environments also take place at higher altitudes because of