Until now, though, little use has been made of drones for marine conservation. Although their endurance, wind resistance and reliability have improved immeasurably over the past few years, the harsh environments and long distances that are integral to marine conservation have raised some serious challenges for drones. At Drone Adventures we are always open to trying something new and willing to push the boundaries of the ‘drones are good’ concept. When Michael Scholl of the Save Our Seas Foundation (SOSF) asked if we were interested in mapping St Joseph Atoll in the Seychelles and collecting imagery for the research projects under way there, we were very curious to find out how drones could help marine conservation.

In late November 2015 we packed up the equipment we needed for a week-long mission on site and prayed to the weather gods to be kind to us and our drones on this risky venture. We needed all the help we could get to map the 25 square kilometres (10 square miles) of St Joseph Atoll and obtain aerial imagery from very low altitude that would reveal shark pups, rays and turtles in the shallow water below.

Our main task was to create a high-resolution base map of the entire atoll, which is approximately eight kilometres (five miles) long and five kilometres (three miles) wide. Our four eBee drones, equipped with consumer-grade compact cameras, would have to obtain overlapping aerial images and we would then have to turn these images into a map, using Pix4Dmapper mapping software. But there are a number of challenges inherent in this undertaking. First of all, water reflects sunlight that interferes with the reconstruction process, so mapping water with aerial imagery by drone has been impossible until now. Secondly, to be able to reconstruct overlapping images, the features that the mapping software detects in order to create the map must be identical from one image to the next. Water, however, has no distinctive features and, with reflecting sunlight making the situation worse, the chances of reconstructing images into a map are close to zero. Featureless sand and dense forest are the next worst things to water when it comes to drone mapping. And, as you’ll have guessed, St Joseph is made up of water, sand and islands with dense forest! This is the main reason that so far few atolls, if any, have been mapped using drones.

Weather was the third challenge. We can plan and prepare for many things, but ideal flying weather is not one of them. Our drones do not like too much wind (stronger than 10 metres per second) or rain, which interferes with the electronics and can result in an emergency landing – not ideal over open water. Both are frequent at St Joseph. We chose the end of November for our mission as weather statistics show that wind and rain are least likely at this time of year. And the weather gods rewarded us with a week of very gentle winds, or none at all, and very occasional rain that fell early in the morning.

Our fourth challenge was the tide. Like the weather, the tide cycle was beyond our influence. We wanted to map the atoll at both high tide and low tide, so the windows for flying the drones and obtaining images were very small.

To create a map with uniform lighting, colours and water level, our best chance was to map the atoll in a very short timeframe, which is why we took four drones so that we could fly them simultaneously and get the images needed in just over an hour. Our flight plans were prepared well ahead, but the challenge lay in flying the drones at the ideal moment: when the tide was just right, when there was little wind and no rain, and preferably not between 11am and 4pm, when there was too much reflection from the sun onto the water. We also had to make sure take-off was from a safe location and that we could maintain radio contact. Thanks to the good weather, we found these ideal moments twice, both during high and low tide, and were able to acquire close to 1,800 images each time.

The images reconstructed perfectly into two maps with a resolution of 15 centimetres (six inches) each, which is about five times more precise than the best satellite map and 10 times better than the Google maps that the local research team had used to date for their daily work. The first analysis using the new maps, conducted by Dr Rainer von Brandis, the scientific director of the SOSF D’Arros Research Centre, enabled him to identify important changes in the shores and sand banks that couldn’t be seen on the Google maps and satellite imagery. Further analysis will enable the scientists to establish details and features of the atoll environment, such as coral reefs, that have eluded them until now due to the low resolution of the maps they were using. In addition, as our maps are not just maps but georeferenced true orthomosaics, the D’Arros research team can now measure distances and features with an accuracy of up to 15 centimetres and locate any spot in the atoll with the same precision, two new possibilities that could be very useful for all future research work on site.

Compared to traditional transects and counts done by boat or on foot, the use of drones brings the important advantage of not interfering with the species’ habitat. Counts done with drone imagery are much more reliable in terms of natural conditions in a specific habitat and are more accurate, as each individual is counted only once and all individuals can be seen over a large area. The lower flying altitude enabled the researchers to identify the shark pups correctly. By zooming in on the image, they could also measure the pups’ length very precisely, as one pixel corresponded to one centimetre. All the images obtained have been left with the D’Arros researchers, who will now sit at their computer screens identifying, counting, measuring and geo-referencing the many shark pups, rays and turtles photographed.

We had some flying time left and, as we are always keen to operate the drones at all times of day and night to gather new information, we asked the researchers to give us some additional challenges. One was to identify the health of trees on one of the islands in the atoll. The scientists had realised that, over time, they were seeing more and more dead or dying trees as they cruised past the island in their boats. They surmise that the rising sea level is pushing salt water into the island’s ground water, but the vegetation is so dense that they couldn’t make out the extent of the dying trees on the island as a whole.

Having equipped one of our drones with a near-infrared camera, we used it to photograph the complete island and then converted the images into not only a map, but also a vegetation index. This index, known as a Normalised Difference Vegetation Index (NDVI), is a simple indicator that can be used to analyse a patch of vegetation and assess whether any of it is living and green. A first quick analysis showed that trees are dying off or are under heavy stress not only at the shoreline, as spotted from the boats, but even more extensively in the island’s interior.

A wide variety of drones is available to bring new perspectives and opportunities to research and nature conservation today. At D’Arros and St Joseph we used senseFly’s eBee drones, a fixed-wing craft that weighs only 700 grams and ensures that flights are easy to plan. It is fully automatic when executing a mapping flight, which gives best results, complete control and great safety. Fixed-wing drones are ideal for mapping large areas and covering long distances, but they are more sensitive to wind and always fly at a constant speed. They were certainly the best choice for the results we were looking for at D’Arros and St Joseph. Copters – either quadcopters or octocopters – are better for spotting a certain type of animal while getting still or video imagery. They come into their own for spotting sharks and whales close to shore or, as happened at D’Arros, for easily finding, filming and photographing manta rays that were feeding just off the beach. Choosing the right kind of drone to fit the mission at hand, weather conditions and the distances to be covered not only guarantees the best results, but also reduces expenses and the risk of, for example, a drone sinking to the bottom of the ocean.

This first marine conservation mission enabled us to test out various applications for drones and produce several baselines for the researchers: a high-resolution map of the complete atoll, vegetation indexes for two islands and aerial imagery at very high resolution to establish undisturbed animal counts for transect and specific research areas. Two of the most important advantages of drone mapping technology are its low cost and the ease of use for just about anyone, both of which allow the same flights to be repeated easily. In addition, the data obtained are converted effortlessly into maps, 3D models or indexes that enable the researchers to analyse accurately the current environment and the changes that occur. Because the results are always very visual (as demonstrated by the stunning map of St Joseph Atoll), they are excellent for communication and in presentations.

Drones are also valuable tools for shark spotters in their daily work. As the technology for both drones and cameras improves, more and more possible applications will be added in the coming months and years. As for us, we are extremely happy that we could provide answers to questions such as ‘Can an atoll be mapped using drones?’ or ‘Is drone imagery good enough for research in the marine environment?’. So when you ask ‘What’s next?’ my answer will be ‘Bimini!’ or ‘D’Arros in November 2016!’ Above all, we want to keep on pushing the boundaries of using drones for marine conservation – and keep on having fun while we do it.