# Testing Procedure of Unmanned Aerial Vehicles (UAVs) Trajectory in Automatic Missions
## 2 Materials and Methods-Test Tasks for UAVs and Field Works
These are the parameters for the UAV that is stabilized in a horizontal position by GNSS and vertical position is stabilized by built-in pressure sensor for the detection of aircraft altitude (GNSS ATTI Mode). Additional parameters of the flight controller include: maximum wind resistance (less than 8 m/s), maximum yaw angular velocity (150\({}^{\circ}\)/s), maximum tilt angle (35\({}^{\circ}\)), and the maximum velocity of ascent/descent (6 m/s). The technical documentation of the on-board computer does not contain information regarding the accuracy of the MEMS sensors that are installed in the IMU [56]. The on-board computers have been installed on DJI Spreading Wings S900 platforms Figure 3. DJI S900 is a hexa-rotor aircraft that is equipped with advanced components (motors, ESC, gimbal, and camera). These vehicles are mostly used for photogrammetric applications. The vehicle maximum take-off weight is 8.2 kg. According to the data that were provided by the manufacturer, it can fly for up to 18 min. (used with a 6S 12,000 mAh battery, on a windless day with a payload of 6.8 kg, hovering at an altitude of 2 m) [57]. On the first part of the tests, there was a light wind with the gusts not exceeding 4 m/s, and on the second part of the tests there was a constant wind with a speed of about 6 m/s, with the gusts up to 10 m/s. The position of the device in space has been measured with the RTS Leica Nova MS50. The polar coordinate measurement system determines the XYZ-position of a moving 360\({}^{\circ}\) mini prism with respect to a certain time stamp while using the three-dimensional (3D)-distance as well as the horizontal  
Figure 3: Location and method of installation of 360\({}^{\circ}\) mini prism on unmanned aerial vehicle (UAV). and vertical angles. The RTS is equipped with servomotors and a moving prism tracking system. According to the data that were provided by the manufacturer, the MS50 operating in a continuous measurement mode allows for the position of a moving object to be recorded at a frequency of up to 20 Hz. The MS50 determines the vertical and horizontal directions with accuracy of 1'' and it makes distance measurements with accuracy of 2 mm + 1.5 ppm in tracking prism mode [58]. During the tests, an average data recording frequency of 5.8 Hz has been achieved. The tracked prism has been mounted on the camera stabilisation controller (gimbal), Figure 3. It allowed for determining the changes in the position of the camera that is the most important from the point of view of the quality of the photogrammetric data being captured. Two measurement points that constitute the measuring base have been placed. Their coordinates have been determined by the static GNSS technology with reference to the ASG-EUPOS network in the geodetic coordinate system 2000, zone 7 (EPSG 2178). One of the control points has been the station of the RTS, the other has served as a reference point. Figures 2 and 4 illustrate the location of the RTS, the reference point, and the UAV take-off point. The arrangement of the individual components of the base has ensured the optimal working conditions for the RTS equipped with an ATR (automatic target recognition) system, which has allowed for the tracking of the prism installed on the UAV. The RTS has been placed higher in relation to the UAV take-off point, on which the 360\({}^{\circ}\) mini prism has been placed. Prior to each measurement (task) starting, a test has been carried out involving an observation of not moving prism for a minimum of 30 s. Thus, it has been possible to assess the accuracy of the measurement that was carried out by the instrument. Spatial deviations from the average position of the fixed prism have not exceeded 15 mm, which, with their standard deviation of 10 mm, have allowed for concluding that the measurement accuracy of this instrument is satisfactory for the testing of the UAV devices equipped with GNSS navigation receivers. UAV takeoff was made after a stable GNSS solution was obtained.