Use of drones in forestry: sustainable management from the air

Aerial images have been used in forestry for decades to perform a variety of tasks, such as forest inventories or mapping damage after disasters. Today, very small unmanned aircraft that can fly autonomously –known as drones – can be employed. Using drones to capture image data enables operations to be planned flexibly and at short notice, thus ensuring that image products are quickly available. Thanks to their low flight altitude, drones can fly even under heavy cloud. Moreover, their quiet and energy-efficient electric motors are not only environment-friendly but also reduce the impact of noise on humans and animals. Equipped with a high-resolution camera or sensors, drones bridge the gap between arduous field surveys on the ground and costly bird’s eye view surveys carried out by manned helicopters or aeroplanes. Their growing success is helped by the fact that the industry’s solutions are becoming more cost-effective and the performance of the flying robots is constantly improving.

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Like helicopters, multicopters can take off and land vertically. They are controlled from the ground by a laptop. With built-in GPS, they are able to maintain their position and altitude or fly to GPS locations autonomously. Depending on the design and weight of the multicopter, the latest models can fly for up to an hour. The camera is capable of swivelling 360 degrees. Thanks to intelligent suspension and flight control, its position is maintained automatically even in windy conditions and a high level of image stability isachieved. The digital images sent live by the multicopter can be “georeferenced”, which means that they can be precisely aligned with existing geographical coordinates. This enables the exact location of any objects photographed to be determined. 3D surface models do not pose a problem either. A number of manufacturers produce video glasses that enable the operator to also “take to the air”. While the drone flies over an object using GPS or sight, the video glasses allow the live image from the camera to be viewed inreal time; the altitude, perspective and display detail can be changed remotely.

Using unmanned aerial platforms enables inventories and surveys to be made of forest land with a hitherto unknown degree of accuracy and significantly extended scope. Their low flight altitude and high degree of independence from weather conditions play a key role here. In addition, results from the flight can be directly incorporated into operational planning.

One major application for drones is the mapping of forests and open fields. The images provided can be used in a timely manner for a wide variety of analyses and applications, such as a health check for plants and trees. This includes the early detection and assessment of pest infestation as well as the determination of moisture levels or the extent of dead wood. The condition of tree crowns, which could previously only be evaluated after a great deal of time and effort, can now be documented by drones in razor-sharp images within just a few minutes. The analysis of water, snow, hail, storm and fire damage is another area in which drones are set to play an increasingly important role in future. Last but not least, the “eye” of the drone is able to quickly and easily locate the position and extent of damage caused by wildlife.

The combination of infrared images and NDVI (normalized difference vegetation index) photos produces images that can be used to measure plant growth, the extent of vegetation and the production of biomass. The simple capturing of forestry conditions also enables reforestation projects to be planned in detail, precisely defining how many plants should be planted in which location and how densely. In the mountains, on the other hand, the construction of skid trails or cableways often presents a major problem. From the bottom of the mountain, it is difficult to judge whether a rock, steep drop or protected tree is in the way. The drone immediately provides a clear result, facilitating rapid decision-making. Unlike conventional image aircraft which can only look down vertically, the drone’s camera can also be tilted, allowing slopes to be recorded precisely. Another increasingly important field of application for multicopters is the observation of climate change. This is an area where forestry can make a key contribution – backed up by digital material – to political decision-making.

According to a study conducted by the McKinsey Global Institute in May 2013, drones – as part of robotics – are already influencing important economic factors such as labour costs, productivity, flexibility and safety. Its efficiency, cost-effectiveness and ease of use open up major future potential for the multicopter. Powered by an environment-friendly electric motor, which results in low noise levels and low emissions, multicopters are an innovation that is perfectly in line with the requirements of contemporary technology. The topic will also be presented at LIGNA 2015 on open-air demo site run by the German Forestry Council (KWF).