## 3 Materials and Methods
### Drone Parameters  
Drones in PA have been mainly used for remote sensing by image gathering. However, drones can be utilized as well for data gathering of nodes deployed on the field. These drones can have fixed or rotary wings, which determines how they fly as well as other parameters such as the ones detailed in Table 1.  
Fixed-wing drones can fly for hours and long distances on a limited amount of energy [40], which makes them popular for Precision Agriculture purposes, including taking pictures of the fields,  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Drone**} & **Nominal** & \multirow{2}{*}{**Cruise Speed**} & **Typical Climbing** & **Max Wind** & **Typical Range** & \multirow{2}{*}{**Wing Type**} \\  & **Endurance** & & **Speed** & **Speed** & **Altitude** & \\ \hline Swinglet [38] & 30 min & 10 m/s & 3 m/s & 7 m/s & 20-500 m & Fixed \\ Phantom 3 advanced [8] & 23 min & 16 m/s & 5 m/s & - & 120 m & Rotatory \\ SenseFly ebee [39] & 45 min & 15.84 m/s & - & - & - & Fixed \\ \hline \hline \end{tabular}
\end{table}
Table 1: Characteristics of commercial drones for PA systems.  
as it provides good autonomy. However, stationary flights are not possible with fixed-winged drones. Furthermore, this type of drone requires a drone catapult to launch it if a person cannot do it, and a big enough surface for landing.  
On the other hand, rotatory-winged drones are the most common. They can stay in one place to perform inspection activities. This type of drone is available with 3 to 8 motors. They can take off and land vertically. However, these drones have less autonomy with endurance below 1 h. Other solutions opt for using their developed drone [41]. This allows detailed customization of the UAV for the required PA solution.  
The intended purpose of the drone will determine its flight plan. For the drone to carry a node that acts as a gateway, the drone must be in the area of coverage of the node long enough for all the data to be transmitted. For small amounts of data, a straight flight plan where the nodes are flown over can work. However, for significant amounts of data, flight plans where the drone circles the node until all the data is transmitted may be necessary [42]. In Figure 1, these two types of flight plans are shown. In the scenario considered in this paper, the flight plan follows straight lines that fly over the nodes deployed on the field. The flight plan that circles the node for a fixed-wing drone or hovering over the nodes for a quadcopter would solve the problem of having enough connection time to perform the connection and transmit all the data before the node is out of the coverage area of the drone. However, as previously stated, in this paper, we consider the challenge presented by the scenario where an imaging drone that has a previously defined flight plan that covers the field following straight lines while carrying the gateway node.  
Furthermore, each country has its regulations for drones. Some countries require obtaining a license that may distinguish between recreational and professional use. The height, areas allowed for flights, and weight of the drone may also be restricted depending on the type of license.