AI News, BOOK REVIEW: Drones for sharks !
- On Monday, February 19, 2018
- By Read More
Drones for sharks !
So when the SaveOurSeas Foundation asked us if we could help them with mapping St-Joseph atoll in the Seychelles and acquiring aerial imagery for the various marine research projects under way in the atoll, we naturally said “Absolutely yes, let’s give it a try!” Even though we couldn’t promise SOSF any results upfront, we were certainly up for the challenge of mapping the 25km2 of St-Joseph and acquiring aerial imagery at very low altitude to detect shark pups, rays and turtles in the shallow water of the atoll.
While it certainly is a paradise for many animal species, it is seemed more like a nightmare when it comes to drone mapping for following reasons: Take-off with a view, from d’Arros with the islands of the St-Joseph atoll in the background Mapping St-Joseph Our first and most important task of the mission lay in establishing a high-resolution map of the entire St-Joseph atoll.
Bursting with hope, we couldn’t wait to unpack our drones and give it a try, hoping that the acquired images will capture the least amount of sun reflection and maximum amounts of underwater features, which would give us a good chance that the images could be reconstructed into a map.
To create a map with uniform lighting, colors and water level, our best chance was to map the atoll in a very short timeframe, reason why we took along 4 drones so that we could fly them simultaneously and acquire the images needed in just over under two hours.
First analysis by Dr. Rainer von Brandis, scientific director of the SOSF D’Arros research center, of the newly created maps allowed for identifying important changes of both island shores and changes in sand banks in comparison to the Google maps and satellite imagery currently used.
In addition, as our maps are actually not just maps but geo-referenced true orthomosaics, the D’Arros research will be able to measure distances and features with a certainty of up to 30cm as well as geo-localize any spot in the atoll with the same precision, two new possibilities that will be very useful for all future research work on site.
Count and measure shark and ray pups With the maps of the atoll in the bag, we were ready to move on to the next goal we set ourselves: flying our drones at very low altitude, 50 meter and possibly lower over the waterline, to acquire aerial images for transects and species analysis.
Preparing for take-off in the middle of the Atoll After some initial test for lowest altitude possible, without having blurry images and risking to sink our eBee’s, we set the ground sampling distance to 1cm which meant flying at approximately 25 meters above the water level.
Put yourself in the researchers’ shoes by counting the sharks in the image above or counting pixels to determine the size of this shark (1pixel = 1cm) below Counting sharks and rays using drone imagery has the advantage of not interfering with the species’ habitat, as is the case in traditional transects and counts done by boat and on foot.
In addition, the sharks, rays as well as turtles identified on the images allow measuring the species size with high precision as 1cm corresponds to 1 pixel, hence zooming in on the image allows to count the number of pixels that make up the pup.
- On Thursday, February 27, 2020
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