Music Good day! The payload can include any device from which you can get different information about the flight or space: Airspeed sensors, ultrasonic and laser altimeters Photo and video cameras, lidars, radars, magnetometers. There are two types of payload: flight payload and mounted payload. Let us talk about the flight payload. This category includes all auxiliary equipment, which increases flight autonomy and safety: Autopilot, Navigation system Air pressure receivers - a system that is used in aviation to determine an aircraft's airspeed, Mach number, altitude, and altitude trend. The most often used in UAVs are Pitot tubes. Ultrasonic rangefinders - used in multicopters to ensure a safe and accurate landing. Infrared rangefinders help to prevent collisions with obstacles. This slide illustrates a cirquit with ultrasonic rangefinders that are used in DGI Phantom 4 UAVs. The mounted payload category includes equipment that allows you to perform production tasks – aerial photography, spectrometry, video monitoring. According to the information obtaining method, payload can be divided into passive and active metods. Passive method – device detects certain signals from the earth's surface – for example, cameras detect reflected sunlight. The active method involves preliminary irradiation of the studied objects - for example, lidar (LiDAR) or radar. Payload types (passive methods): RGB cameras, NIR-band cameras, UV cameras, Photo and video thermal imagers, Hyperspectral cameras, Gamma spectrometers, Magnetometers and others. Let us discuss RGB-photocameras. RGB cameras are the most popular payload. They differ in the following parameters: Size of the matrix; The effective resolution of a matrix, number of pixels; Shutter - Central or slit. Serious requirements are imposed on the camera lens, because it is the main thing that affects the optical distortion of the picture. Lenses differ in aberration, amount of blurring, distortion. Well-known manufacturers of cameras: Sony, Leica, PhaseOne. RGB cameras are used for: Orthomosaic creating, Shooting high-rise objects, 3D-models creating. NIR-range (near infrared) cameras are widely used in forestry and agriculture. They provide information about vegetation state, since chlorophyll in plants reflects light in the NIR range. Largely, the characteristics of NIR and RGB cameras are similar. Basically, NIR and RGB cameras are combined into a single device with channel diversity. Hyperspectral cameras differ from multispectral ones in a large number of channels - up to 450. Each channel is a narrow band with a spectral resolution of 1.3 nm to 5 nm. Hyperspectral cameras are used for geological exploration, environmental surveys, and forest taxation work. Thermal imaging cameras produce pictures based on infrared radiation of objects, which makes it possible to obtain information at night or to find objects by indirect signs (thermal trace of heating mains). There are different temperature determining methods: Absolute and Relative. Magnetometer is an instrument system that measures the characteristics of the Earth’s magnetic field. Magnetometer usage makes possible to find ore bodies in the thickness of the earth. Mostly used in geological exploration. This slide illustrates payload types based on active methods: LiDAR and Different types of radars. Consider LIDAR. The word LIDAR is an abbreviation - Light Identification Detection and Ranging. It must be emphasized that the word light is used, since there is a slight misconception that scanning from LIDARs is a laser scannig. In fact, in modern systems based on UAVs, lasers are practically never used - other light sources are used. In the picture you can see the LIDAR working scheme. We have a source and a receiver, as illustrated in this figure. The source generates a signal and sends it to the object. A part of the signal is returned (it is never 100%) and the receiver reads this information. There are various methods for determining the distance to an object. Let us consider the various types of LIDARs usually installed on UAV. The table shows several options from various manufacturers. They differ in such characteristics as the scanning speed (the number of dots per second that this LIDAR is capable to receive), the maximum distance to objects, the number of reflections, weight and, of course, cost. The number of scan points greatly depends on the speed of rotation of the LIDAR and the number of emitters and receivers installed in it. There are usually several of these, to increase efficiency. The power of these sources directly affects the range. Modern LIDAR systems usually operate at a range of 200, maximum 300 meters. The number of reflections is one of the important parameters, it is the main advantage of LIDARs over other systems. In fact, it is the ability to receive several reflections from objects per one impulse. What does it mean? An impulse is emitted and moves towards, let's say, a tree with foliage. Part of the impulse is reflected from, for example, a leaf, and part of the impulse moves on. This part is reflected from another leaf or other obstacle and so on until the power of the last reflected signal reaches a certain threshold value. This value is different for each LiDAR, but usually 10% of the initial pulse power. Thus, in the most advanced systems, an almost infinite number of reflections per pulse can be obtained. In more primitive systems that are installed on UAV, this number is usually limited to two, maximum three. If there are two, then this is usually the first reflection and the last. The most recent reflection is usually taken as reflection from the earth's surface. So, there is no magic in penetrate foliage, this is not an X-ray, the secret is several reflections per one impulse. It is also worth mentioning that only one company (Riegl Company) (you can see it in the slide) develops systems special for UAVs. . All the other LiDARs that are shown here, in fact, came from the field of unmanned vehicles (cars), which is now very actively developing. These devices allow an unmanned car to drive autonomously. Since the weight of these devices is already quite small (about 1 kg), and miniature gyroscopic systems have also been developed that allow the gyroscope to be placed on a 3x3 cm board, their combination allows scanning from the UAV. This slide shows a picture that compares two technologies. They are the photogrammetric technology and the LiDAR scanning technology. As we see, in difficult areas (usually a forest, bushes or tall grass), photogrammetric technology does not show good results. It is able to get relief data only where there are large enough glades or other open areas. It is clear that the quality of the relief obtained using photogrammetric technology will not be very high. LiDAR, as you can see, allows you to "penetrate" under the foliage - I have explained the mechanism earlier - and provides reflection from the earth's surface. But we can’t immediately say that LiDAR is much better, and let's all of us use LiDARs. There are limitations on mass and, more importantly, cost, and in certain areas, photogrammetric technology works better and, most importantly, it is cheaper and more productive. Therefore, these are two technologies that are often called upon to solve similar problems, but they have their own strengths and weaknesses. Today we have discussed the various types of payload that can be installed on the UAV. Of course, this is not an exhaustive list, but certainly the most popular ones are mentioned. Further we will consider aerial photography implementation using fixed-wing UAV equipped with RGB camera.
