# Development of a Robotic Airboat for Online Water Quality Monitoring in Lakes
## 4 Materials and Methods  
Before the construction of the hull, some models (hydrofoils, catamaran, trimaran, and winecup) was studied, because the hull should house all components, besides presenting resistance and floatage. The chosen hull was the winecup model, because it has an internal space to house all electronic components. For this, it was designed as an aluminum base structure, 1.10 m long and 0.33 m wide at the stern, with decreasing width as it approached the bow. To cover the aluminum frame, a high-density cardboard was used for a better format design.  
However, since cardboard is a hydrophilic, easily deteriorated material, a coating with epoxy resin and glass fiber was used to provide rigidity and to protect the structure from possible collisions with obstacles, during navigation (mission). The fiberglass mat was sized, according to the total hull volume of the boat. Each epoxy lamination process took approximately 15 min to work, after mixing with the catalyst. In this process, two layers of fiberglass mat was added.  
After the lamination process, a layer of plastic mass was added to correct the imperfections, then its surface was sanded all over and an automotive paint was applied.  
For the monitoring and collection of the physicochemical parameters of water (pH, Dissolved Oxygen, Oxidation-Reduction Potential), a sensor and probes material was acquired. They were responsible for analyzing their respective parameter, transform it into digital information, and send it to the microcontroller, in a predefined time interval. Once the data of all sensors were collected, a protocol was formatted and sent to the Raspberry Pi board, through the USB port (Universal Serial Bus). From the analyzed kits, the Atlas Scientific EZO TM Class Circuit (Atlas Scientific LLC, Long Island City, USA) was chosen, for having an affordable price, in comparison with the others and for its stability in sensor reading.  
Inertial Measurement Unit (IMU) is an electronic circuit that measures the forces suffered by a body attached to it, such as angular velocity, acceleration, and the magnetic field, using a combination of accelerometers, gyroscopes, and magnetometers. They are widely used in aircraft, drones, cruise missiles, Unmanned Aerial Vehicles (UAV), and Unmanned Space Vehicles (USV). In this project, the IMU was used together with the GPS, to determine the location, displacement, and direction of the estimated autonomous navigation. Some models of IMU were researched on, such as the MPU6050 and the MPU 9150, but the GY87 (Kuongshun Electronic, Shenzhen, China) was chosen because it had some characteristics similar to the previous ones and also had a lower cost.  
GPS is a satellite positioning system that provides the Latitude and Longitude, as well as other information, such as speed, date, time, and altitude, at any point on Earth. GPS is used in aviation and maritime navigation and is currently used by people who practice some extreme sports in places far away and difficult to reach, or even for urban transport [28]. To collect these data, the BU-353S4 USB module (GlobalSat WorldCom Corporation, New Taipei, Taiwan) was used.