Unmanned aerial vehicles as a useful tool for investigating animal movements - samples

We surveyed 8 to 10 November in 2019, from 21:00 to 5:00, to collect data on wild boar movements. The survey was conducted nocturnally with the intention of allowing the ambient temperature to drop and because wild boars were known to be nocturnal in Ishibashi district. An Inspire 1 UAV equipped with a Zenmuse XT thermal camera (FLIR Systems, Inc., Wilsonville, Oregon, United States) was flown manually in areas where wild boars were likely to be present. The weight of UAV, including the thermal camera, was 3,115 g. Inspire 1 is a quadcopter UAV with DJI 1345T (SZ DJI Technology Co., Ltd) propellers. The diagonal dimension without the propellers in landing mode is 581 mm. Zenmuse XT is an uncooled Vox microbolometer with 640*512 resolution, 17 μm pixel pitch, 13 mm focal length, and 7.5 to 13.5 μm spectral band. We used the DJI GO (application, SZ DJI Technology Co., Ltd) installed in an iPad Pro(Apple Inc., Cupertino, California, United States) as a screen to monitor the flight, which showed the image from the camera in real-time. For this reason, an internet connection was required during the survey. We prepared eight batteries (TB48, SZ DJI Technology Co., Ltd), but we had to charge the batteries while conducting the flights. We overcame this issue by carrying an emergency battery capable of 100 V AC output. We flew the UAV approximately 50 m from the ground. This was because we wanted to avoid disturbing the animals, and we were able to distinguish boars and other species according to their body size and shape. The data were collected as videos, and once we detected a boar, we flew the UAV right above it, ensuring that the boar was in the centre of the tablet’s screen. Then we let the UAV hover (until the UAV emitted a low-battery signal). To make it easier to calculate the distances from which the boars moved, we recorded the videos with the camera facing the ground perpendicularly, as if it were a fixed-point camera in the sky.

本研究于2019年11月8日至10日的21:00至次日5:00开展野外调查，以收集野猪活动相关数据。本次调查选择夜间开展，一方面是为了等待环境温度降低，另一方面是因为石桥区（Ishibashi）的野猪具有夜行习性。搭载禅思Zenmuse XT热成像相机（FLIR系统公司，FLIR Systems, Inc.，美国俄勒冈州威尔逊维尔）的Inspire 1无人机（Unmanned Aerial Vehicle, UAV），在野猪大概率出没的区域进行手动操控飞行。该无人机（含热成像相机）总重量为3115克。Inspire 1为四旋翼无人机，配备DJI 1345T螺旋桨（深圳大疆创新科技有限公司，SZ DJI Technology Co., Ltd）。着陆模式下未安装螺旋桨时，其对角线尺寸为581毫米。禅思Zenmuse XT热成像相机采用非制冷Vox微测辐射热探测器，配置参数如下：分辨率640×512，像素间距17μm，焦距13mm，光谱波段7.5至13.5μm。我们通过安装于iPad Pro（苹果公司，Apple Inc.，美国加利福尼亚州库比蒂诺）上的DJI GO应用程序（深圳大疆创新科技有限公司，SZ DJI Technology Co., Ltd）作为监控屏幕，实时显示相机传回的影像以监控飞行状态。因此，本次调查过程中需要保持网络连接。我们准备了8块TB48型号电池（深圳大疆创新科技有限公司，SZ DJI Technology Co., Ltd），但飞行作业过程中仍需对电池进行充电。为此我们携带了一台可输出100V交流电的应急备用电源，以此解决该问题。我们将无人机飞行高度控制在距地面约50米处，此举一方面是为避免惊扰野生动物，另一方面我们可通过体型与外形区分野猪与其他物种。本次调查以视频形式采集数据，当探测到野猪时，我们会操控无人机飞至野猪正上方，确保野猪处于平板屏幕的中心位置，随后保持无人机悬停直至其发出低电量警报信号。为便于后续计算野猪的移动距离，我们将相机垂直朝向地面录制视频，模拟空中定点相机的拍摄视角。