## 3 Prototype Description and Implementation
### Assembly of the Prototype System  
As described before, it was required that the UAV had a GNSS signal reception system, so a choice had to be made between a controller with an integrated GNSS signal reception system or integrating one that would always indicate the position of the UAV to the operator. In this case, the first option was chosen since, besides being more efficient for it to be integrated into the controller due to space and aerodynamics, it was also more efficient for communications bandwidth between the base station and the controller. As already explained in chapter 3, the controller chosen for the project has been the Navio2, which is characterized as a HAT (Hardware Attached Top) for the Raspberry Pi board used to integrate the hardware components. It must be noted that Navio2 that has several precision sensors, as well as an integrated GNSS signal reception circuit. The Operating System installed on the Raspberry Pi is a preconfigured distribution of Raspbian, which is the recommended Operating System for Raspberry based on a Debian GNU/Linux distribution [49]. To install it, it is only necessary to download the preconfigured image from the Navio Emlid tools website and install the microSD card that will later be inserted in the Raspberry Pi. Once the installation process of the operating system has been completed, it was necessary to edit the _wpa_supplicant.conf_ file (which is in the/boot directory) to configure the Wi-Fi network where the ground control station must be found for subsequent communication with the aircraft (in this case, the UAV). Once the Raspberry Pi was connected to a Wi-Fi network, it was also possible to connect to it through the Secure Shell protocol (SSH) so that the configuration of the UAV will be completed. Afterwards, the UAV was assembled by mounting the components described in the third chapter. Figure 10 displays the result of the UAV with all its components fully assembled. The blue box located in the center of the UAV is the Navio2 controller; the GPS antenna (black) and the video transmitter antenna (blue) can be seen as well. Figure 10: Assembled UAV. The UAV is now ready to be configured through the Mission Planner software. However, to perform this task, there must be a Wi-Fi network to which both the Raspberry Pi of the UAV and the CGS that runs the software are connected. To configure the UAV, the battery must be added to the UAV by the port enabled for it once the connection to the Wi-Fi network of both the Raspberry Pi and the CGS has been established. From this point, the Raspberry Pi Operating System will boot and the Arducopter software will start. The first step that must be carried out is the process of \"binding\" (pairing) or establishing a connection between the radio control transmitter and the receiver on board the aircraft. Here, a communication channel between the transmitter and the UAV is created the first time that communications between both entities are set (it is only necessary to do it in the initial configuration since in future occasions the connection will be established automatically) by updating the transmitter to the latest version of the OpenTX software, as this it is necessary to connect the transmitter to the computer via the USB cable. Prior to this step, the latest version of OpenTX Companion software must have been installed on the computer. Once all the necessary software has been installed, the station must be turned on in bootloader mode. After switching on the transmitter in bootloader mode, it must be connected to the computer via the USB cable. Afterwards, the following procedures must be carried out according to the hardware built specifically for the purpose of this system:  
1. The Radio Controller module must be configured. To do so, the software used in such controller might have to be updated. This is required in case there are new functionalities that improve the usefulness of the Radio Controller itself. 2.