# A Review of Flying Ad Hoc Networks: Key Characteristics, Applications, and Wireless Technologies
## 2 UAV Classification
By applying ML techniques to real-time data gathered by UAVs, parameters such as plant disease detection and soil moisture [37], minimum and maximum temperatures at field level [38], and the level of phosphorus in the soil [39] can be predicted. Using UAVs in agriculture can reduce costs as well as potential pesticide exposure to workers. Of the numerous types of agricultural drones on the market, among the most widely used are the _PrecisionHawk DJI Matrice 200 v2_ ([[https://www.dji.com/br/matrice-200-series-v2](https://www.dji.com/br/matrice-200-series-v2)]([https://www.dji.com/br/matrice-200-series-v2](https://www.dji.com/br/matrice-200-series-v2)) accessed on 21 July 2022), the _senseFly eBee SQ_ ([[https://www.sensefly.com/blog/talking-ebee-sq-agriculture-drone/](https://www.sensefly.com/blog/talking-ebee-sq-agriculture-drone/)]([https://www.sensefly.com/blog/talking-ebee-sq-agriculture-drone/](https://www.sensefly.com/blog/talking-ebee-sq-agriculture-drone/)) accessed on 21 July 2022), and the _Sentera PHX Complete System_ ([[https://sentera.com/data-capture/phx/](https://sentera.com/data-capture/phx/)]([https://sentera.com/data-capture/phx/](https://sentera.com/data-capture/phx/)) accessed on 21 July 2022). * _Wireless Coverage (Figure 2, box D)_: UAVs that are equipped with directional antennae are used to provide wireless coverage for both indoor and outdoor users in dense environments or when terrestrial BSs are out of service due to bad weather conditions [40]. However, there are outstanding issues, such as finding the minimum number and optimal deployment of aerial wireless BSs or cellular-connected UAVs to maximize the total coverage area. Moreover, providing an optimal A2G path loss model is required for aerial wireless BSs [41; 42; 43]. * _Environment and Climate (Figure 2, box E)_: UAVs can be used to help the environment in a wide variety of way; Figure 2, box E shows applications of UAVs in the mining industry [44; 45], aerial mapping, nature monitoring [46; 47; 48], wildlife protection [49; 50], forest fire detection [51], prediction of rising sea levels [52; 53], renewable energy maintenance, disaster relief [54], climate change forecasting [55], the potential of space drones for exploring other planets [56], marine drones that can study marine organisms and identify the location of oil spills [57], tree-planting, clean energy, and solar power generation [58; 59]. * _Delivery and transportation (Figure 2, box F)_: As shown in Figure 2, box F, delivery UAVs can be used to transport food, medical supplies, household items, and packages, as well as for ship resupply [40; 60]. The Federal Aviation Administration (FAA) has proposed airworthiness criteria for type certification of delivery drones for commercial operations, which in 2020 covered ten drone manufacturers, Amazon Prime Air, Zipline, and Wingcopter among them ([[https://www.faa.gov/newsroom/faa-moving-forward-enable-safe-integration-drones?newsId=96138](https://www.faa.gov/newsroom/faa-moving-forward-enable-safe-integration-drones?newsId=96138)]([https://www.faa.gov/newsroom/faa-moving-forward-enable-safe-integration-drones?newsId=96138](https://www.faa.gov/newsroom/faa-moving-forward-enable-safe-integration-drones?newsId=96138)) accessed on 21 July 2022). * _Construction (Figure 2, box G)_: In construction applications, UAVs can be utilized for technical inspection, painting, safety, and delivery. _Inspector UAVs_ equipped with high-resolution digital cameras are employed for progress monitoring, technical inspection of construction sites and buildings, and quality control [60; 61]. _Delivery UAVs_ with high-performance rotors and robust frames are used to carry material, tools, and payloads to workers at heights. _Builder UAVs_ can be connected to paint reservoirs and onboard compression pumps for painting applications, and _Safety UAVs_ with infrared and visual sensors are used to monitor and detect safety issues in construction [62; 63; 64].