# Data Collection in Areas without Infrastructure Using LoRa Technology and a Quadrotor
## 2 System Description  
This article proposes a low-cost solution for the acquisition and transmission of water quality data through a system of monitoring stations and a UAV to access the data from the stations (see Figure 1). The UAV is used as a mobile data collector and network manager. One of the critical characteristics of LoRa is its unique modulation, which allows its coexistence and operation with other RF technologies [14]. So, the use of this type of transmission is suitable for interactions with the UAV and its multiple modules, which usually use different types of UHF transmissions [15]. In addition, this article proposes the use of a UAV with a short-range transceiver so that, through periodic trips, the information sensed by the stations can be collected. In addition, the speed and altitude conditions of the UAV that are required for high-quality data transmission are shown. It is essential to highlight that, in this proposal, we do not consider challenges such as optimal deployment, energy-efficient use, and movement restrictions of UAVs, which are areas of opportunity [16; 17]. The operation of water quality monitoring stations is based on three stages: measurement of the desired variables, data processing, and data transmission. These tasks are carried out in three different Python programs: Sensors, File Manager, and Sender, respectively. For this work, the measurement of the water's temperature, turbidity, conductivity, and dissolved oxygen variables are considered (see Figure 2). The UAV is responsible for collecting data from the stations that are located along its route, and then the system uploads the collected data to a cloud database. Successful communication between the stations and the UAV is achieved by synchronizing the REYAX KYLR896 transmitters. Figure 1: Oceanographic data collection system by an unmanned aerial vehicle. Figure 2: Monitoring system diagram. Once the data recorded by the stations have been collected and the UAV trajectory has been completed, it is necessary to upload the data to a database for visualization in a web application. For this purpose, a connection is made to a Firebase database hosted on the Google service. This program generates a connection with the Firebase database and uploads the data collected from each station. This is performed when the UAV has an Internet connection. Therefore, in this paper, we propose using a commercial UAV, a short-range transceiver, and a Raspberry Pi Zero card to collect information sensed by the stations. In addition, the experimental results show adequate transmission depending on the speed and height of the UAV, with which good-quality data transmission is guaranteed. It is essential to mention that there are some prototypes for buoys that take water quality and meteorological readings, such as [11; 12; 18; 19], which motivates the development of this work and its possible application in similar prototypes. The works mentioned above have focused on remote communication between buoys and a ground station using different communication technologies, such as high-frequency radio signals, GSM, Zigbee, WiFi, and LoRa [2]. However, the range in which buoys can be located is limited by the coverage of communication technologies [20]. Therefore, this work aims to serve as a basis for the development of maritime applications in which buoys are used for monitoring oceanographic variables, the main areas of opportunity being as follows:  
* Expanding the positioning distance of buoys limited by wireless communication technologies. * Establishing communication protocols between buoys and a data collection system that guarantee the correct transmission of information. * Using a UAV and IoT technology to collect the information stored and packaged in the buoys during different intervals. * Delimiting the maximum distance of the buoys based on the flight path of the UAV and the performance of its flight autonomy.