Until quite recently, aerial photography required the use of manned planes and helicopters and was prohibitively expensive. Rapid advances in unmanned ‘drone’ technology, however, are dramatically increasing the possibilities for use of aerial photography in field investigations. Due to the low altitude at which they can be flown, they offer aerial imagery at levels of resolution unthinkable for satellite imagery (for now). As such they present huge potential for monitoring remote areas of forest, whether for monitoring biodiversity or illegal logging.
Drones (also known as unmanned aerial vehicles or UAVs) can be divided into two distinct types: fixed wing drones and quadcopters. The former are more expensive, require more skill, are relatively complex to deploy, but can cover large areas. The latter are cheap, easy to use and quick to deploy, but have limited range. Generally speaking, fixed-wing drones have to-date been used in forest monitoring for mapping, while quadcopters have predominantly been used as more simple documentation tools. The use of drones is increasingly, and quickly, being regulated in many countries. Investigators should check the current local legal situation before using them in any given country.
Since at least 2012, conservationists have been trialing the application of fixed-wing UAVs for remote monitoring. These lightweight, flying vehicles can host cameras and a GPS device, taking geo-referenced images, making them a very effective tool for monitoring remote and inaccessible areas. They can be flown along pre-determined routes or with a remote control, and cover 100 km per trip.
Unlike quadcopters (see below), fixed-wing drones suitable for use in forest monitoring cannot be purchased ‘off-the-shelf’ but usually require some adaptation of products on general sale. Their use also requires extensive knowledge and practice. However, a lot of advice is available on the internet, and specialist organisations such as Conservation Drones exist which can help. As a result, fixed-wing drones are becoming increasingly affordable and accessible to grassroots NGOs or even communities, for monitoring of their territory. In 2014, the Sumatran Orangutan Conservation Programme and Conservation Drones flew two flights separated by a few months over the Gunung Leuser National Park. The imagery they obtained, which is georeferenced, shows evidence of illegal logging that may not have been visible during fieldwork or foot patrols, even close to the area. The evidence was presented to park officials who took action to stop the logging.
The past three years have seen a dramatic increase in sales of small remote-controlled quadcopters, with mounted cameras.
Quadcopters are affordable and extremely easy to use. A wide range of models of differing levels of capability are readily available to purchase ‘off-the-shelf’ and can be used in forest monitoring without special adaptations. With a morning of reading and an afternoon of practice, most users can become fairly accomplished. They lack the range of fixed-wing drones, but make up for this with ease of deployment and the ability to hover over areas of interest. Most often they will be guided by eye, using a remote control, in contrast to the pre-planned routes flown by drones. This will lead to a less comprehensive coverage of an area, and the imagery they produce may not be geo-referenced.
However, as an auxiliary tool to fieldwork they can be invaluable. They can be deployed within minutes and offer a birds-eye view of conditions on the ground. They can be used to view sawmills or logging operations from a reasonably safe distance. Like drones, their routes can also be plotted out by adding some basic software to the kit.