purposes and will be more for research & military tech, and would be costly [15].
1.3.4.7 Flight Parameters Through Telemetry
Nearly all drones have a Ground Station Controller (GSC), allowing the remote controller to fly the drone and keep track of the current flight telemetry. Telemetry data on the remote controller may include remaining battery power, warnings, speed, height, UAV range, GNSS strength, and video.
1.3.4.8 Drone Security & Hacking
UAV in many ways is a kind of flying computer with an operating system, flight controllers, and other boards with programmable codes, they can also be hacked into. There are Drones that have been developed to fly around seeking other drones and hacking into the drone wireless network, which then disconnects the owner and takes over that drone. However, there are some ways to protect your drone from hackers [17, 18].
1.3.4.9 3D Maps and Models With Drone Sensors
Multispectral, LIDAR & Photogrammetry sensors are used to build 3D models of landscapes and buildings. Thermal vision and low light night vision sensors are used by drones to scan landscapes, building to assist in agriculture, search & rescue, firefighting, and so on.
A technology called Sensor Fusion can be used in drones in which drones carry different sensors with software combining the data together for better results. These systems automatically combine input data from several different sensors such as regular RGB camera, thermal camera for the purpose of improving system performance or application. Combining data from multiple sensors reduces and corrects the errors as compared to using individual sensors to calculate the accurate position and orientation information. For e.g. Multi-Spectral sensors in drones can create Digital Elevation Maps (DEMS) of land areas to provide precise data on flowers, shrubs, trees, fauna, and on the health of crops or more.
Drones with Time-of-Flight (ToF) sensors came to the market in 2016. ToF is also called Flash Lidar which can be used on its own or can be combined with RGB and regular LIDAR sensors to provide economical solutions across various sectors. ToF depth ranging camera sensors can be used for 3D photography, tracking objects, measure volumes, object scanning, obstacle avoidance, indoor navigation, gesture recognition, gesture recognition, augmented reality games, and much more. These Flash LIDAR ToF cameras have a huge advantage as it can measure distances to objects within a complete scene in a single shot. In photogrammetry and lidar mapping, the UAV is programmed to fly over an area autonomously, using waypoint navigation [19]. The camera on the drone will take photographs at a continuous interval like every 0.5 or 1 s then these photos will be stitched together using specialized photogrammetry software to create 3D images as shown in Figure 1.8.
DroneDeploy is a widely used 3D mapping software. It’s a mobile app and a live map is being used in various sectors for creating 3D models and maps. Their specific software solution for the agricultural sector and others work with most of the latest drones.
Figure 1.8 Visual representation of a fixed-Wing platform taking photographs at its designated points [39].
Capturing high-resolution images on a drone that is stabilized is important and using top photogrammetry software to process them into real maps and models is just as important. Some of the top drone mapping softwares are as follows:
• Autodesk ReCap Photogrammetry Software.
• Pix4D-Mapper Photo-grammetry Soft.
• Drone-Deploy 3D Mapping Solutions.
1.3.5 UAV Communication Network
The unmanned aircraft system (UAS) or UAV is facing enormous growth from capital as well as the technological point of view. The number of drones in operation is increasing in gigantic number, with several million produced annually in recent years. The scale and mass of drones vary from micro-drones weighing a few grams to heavy gigantic machines as big as the size of almost a commercial aircraft.
According to ICAO (International Civil Aviation Organization), UAS has been classified broadly into two categories:
• Remotely-piloted Aircraft systems: It consists of various elements which include unmanned aircraft, ground control & some necessary command and control links, or any other element which is configurable together and is required for flight operation.
• Autonomous aircraft: It is an unmanned aircraft which don’t require pilot involvement in the controlling or management of the flying aircraft [20].
Communication is a key aspect of the UAS system due to the presence of a human in a remote place. Therefore, the operation of UAS depends upon communication which enables safe UAS operation in non-segregated airspaces.
1.3.5.1 Classification on the Basis of Spectrum Perspective
International Telecommunication Union (ITU) classifies unmanned aircraft broadly in three categories on the spectrum perspective. It is highly dependent on the range, cruise speed, and altitude of the unmanned aircraft. The Table 1.1 depicts the same classification [21]:
Table 1.1 UA categories on the basis of spectrum perspective.
| Category of unmanned aircraft (UA) | Weight (kg) | Maxim height/ altitude (m) | Cruise speed (km/h) | Endurance (h) | Maximum range (km) |
| Small | <25 kg | <300 m | <111 km/h | <5 h | Visual LoS <3 km |
| Medium | 25–2,000 kg | 300–5,500 m | 111–185 km/h | 5–30 h | RF LoS 150–250 km |
| Large | >2,000 kg | >5,500 m | >185 km/h | >30 h | BeyondRF LoS |
1.3.5.2 Various Types of Radiocommunication Links
For the safe operation of unmanned aircraft under Beyond LoS (Line-of-Sight) and Line of sight
