# Testing Procedure of Unmanned Aerial Vehicles (UAVs) Trajectory in Automatic Missions
## 3 Results
### Task 1--Determining the Hovering Accuracy by the UAV  
The analysis of the data has been commenced by preparing graphs of the changes of the coordinates that have occurred during the test. Figure 5a presents a graph of the changes in the UAV location coordinates in time: recorded by the MS50 instrument, from the LOG file, and the value designed for the COM-2 on-board computer during the strong wind test (the test under the strong wind conditions). This Figure demonstrates the changes in the position of the device, separately for the coordinate components: North (N), East (E), and Altitude (A), relative to the take-off point during the entire test. Figure 5b presents similar graph, but during a 120-s part of the test. In all of the missions carried out as part of this task, two regularities have been noticed. The first one has involved small-range changes of the UAV position, from about \(\pm\)0.3 m along the \(X\) and \(Y\) axes to about \(\pm\)0.5 m for the altitude. Depending on the conditions, the duration of these changes has been 10-20 s. The second regularity involved location changes with larger values, being distributed over longer intervals of about 60-120 s. Firstly, the obtained values result from the adjustments taken into account by the device, obtained from the gyroscopic sensors and inclinometers installed in the IMU, and secondly by the indications that were derived from the GNSS system. Table 1 summarises the data on the differences calculated between the different types of the captured data. The maximum and minimum differences, denoted as MIN and MAX, respectively, their range MAX-MIN, the mean value of the difference \(\overline{X}\) and the standard deviation of the coordinate differences \(\sigma\) are presented:  
\[\overline{X}\ =\ \frac{\sum_{i=\ 1}^{n}x_{i}}{n} \tag{10}\]  
Figure 5: Changes in UAV position in time for task 1 for North (N), East (E), and Altitude (A) coordinate components, relative to place of take-off: (a) during the entire test, (b) during a 120-s part of the test. \[\sigma = \sqrt{\frac{\sum_{i_{i}=1}^{n}\left(x_{i}-\overline{X}\right)^{2}}{n-1}} \tag{11}\]  
where \(x_{i}\) are the observed values of the sample items, \(\overline{X}\) is the mean value of these observations, and \(n\) is the number of observations in the sample. The MAX-MIN parameter in the PROJ-MS50 and MS50-LOG combinations for both on-board computers indicates that the equipment has been positioned with the accuracy resulting from the characteristics of the GNSS systems. Both of the on-board computers show low differences in LOG-PROJ calculations. The drift of the device position during the whole test has been also recorded by the MS50 instrument. It has been observed in the recorded altitude and in the horizontal position during the tests that were performed in strong wind conditions. The values of the drifts for each axis, for each of the tests, have been determined by fitting linear regressions into the time series. Table 2 presents the values of the time drifts calculated for all tests for each coordinate component. The values of the drifts determined for the indications obtained from the LOG files of the on-board computers have also been added. It should be noted that both devices tested while hovering, have performed slight horizontal movements related to the compensation of wind gusts. In strong wind, the difference between the extreme values of the position (MAX-MIN) is rather greater than for a light wind Table 1. Similarly, standard deviations of the differences are also slightly greater. As far as the altitude data is concerned, in none of the tests has the UAV reached the planned altitude. The average position of the UAV for COM-1 in light wind has been 1.32 m lower, and during the remaining three tests it has exceeded 3 m. The drift of the value of the device position in time has also been recorded by the external surveying instrument MS50 Table 2. Drift is most clearly visible for the vertical position. The horizontal drift in time has mostly occurred in windy weather conditions.