UAV-based ALS for New Zealand Plantation Forestry: Challenges and Opportunities
As management costs increase, managed forest resources get larger, and our available labour force declines, foresters have been increasingly harnessing the advantages of remote sensing. In recent years, LiDAR has emerged as a crucial tool in remote sensing for foresters, and has emerged to become one of the go-to methods for taking inventory of forest resources, mapping forest boundaries and monitoring forest growth. With the advent of UAVs and the coming of the “Drone Age”, airborne laser scanners (ALS) have been miniaturised and adapted to fit the tiny, unmanned craft, and a number of early adopters rose to the challenge of exploring the uses for this new platform. Scion was one of these early adopters in New Zealand, and as the national Forest Research Institute, set about assessing the benefits of the new technology for the forest industry. This task has had its challenges. After a generous learning curve in flying the unit, and an initial burst of data capture, it soon became apparent that there was a lot more to capturing this data and analysing it than was first envisaged. Forestry is also a very challenging environment for UAV operations, with the nature of our areas of interest being tall, and closely packed in. Plantation forestry consists of vast areas of tightly packed uniform trees, offering only narrow forest roads and landings for take-off and launch sites. Mature radiata pine trees can reach heights of up to 60m tall, and often exceed 15m by age 12. In addition to this, NZ forests are often planted on the land that was too steep for agriculture or dairy, and so often presents very complex terrain for UAV operations. These factors all combine to make VLOS (Visual Line of Sight) difficult or impossible in many situations. It is also an environment that is prone to attenuation of communication signal, making the remote operation of crafts difficult or challenging at best. Now, three years into our research, Scion want to share some of the pitfalls and progress, opportunities and challenges that have faced the team, and also share their opinions on the future of this technology and where it may lie for the forest industry. We will describe from our experience how to select suitable craft and sensors, integrate them, mitigate operational challenges, and discuss post processing to obtain data sets for analysis. We will also discuss the applications that UAV ALS can offer to forestry, along with a glimpse into what the future could hold. As the technology improves, not only in the sensor space, but also in the platforms used to carry them, and the flight control software, the application of this technology to forestry is becoming more feasible.