# Quality Analysis of Unmanned Aerial Vehicle Images Using a Resolution Target
## 4 Results
### GSD Analysis  
Table 3 presents the results of the GSD analysis using the bar target. The flight height, camera focal length, and pixel size were used to calculate the theoretical GSD, which was compared with the measured GSD. Theoretical GSD can be calculated by multiplying the camera's one-pixel size by the flight altitude and dividing by the focal length. In this context, the measured GSD deviates from the theoretical GSD, owing to errors in the correction values of the camera, the atmospheric conditions during image capture, the unmanned aerial vehicle's dynamics, GPS error values, and other factors.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Camera Model** & **Flight Height** & **Overlap** & **Area** & **Number of Images** & **Wind Velocity** & **Flight Date** \\ \hline a6000 & 150 m & \begin{tabular}{c} P = 60\% \\ Q = 75\% \\ \end{tabular} & 720 m\({}^{2}\) & 451 & 0.9 m/s & 19 April 2011 \\ \hline FC 6520 & 150 m & \begin{tabular}{c} P = 60\% \\ Q = 70\% \\ \end{tabular} & 422 m\({}^{2}\) & 371 & 1.9 m/s & 18 May 2022 \\ \hline FC 6310 & 100 m & \begin{tabular}{c} P = 60\% \\ Q = 70\% \\ \end{tabular} & 894 m\({}^{2}\) & 632 & 1.9 m/s & 18 May 2022 \\ \hline iXM-100 & 200 m & \begin{tabular}{c} P = 60\% \\ Q = 70\% \\ \end{tabular} & 894 m\({}^{2}\) & 556 & 1.9 m/s & 18 May 2022 \\ \hline  & 150 m & \begin{tabular}{c} P = 60\% \\ Q = 70\% \\ \end{tabular} & 894 m\({}^{2}\) & 422 & 1.9 m/s & 18 May 2022 \\ \hline iXM-100 & 150 m & \begin{tabular}{c} P = 60\% \\ Q = 70\% \\ \end{tabular} & 462 m\({}^{2}\) & 231 & 1.3 m/s & 19 March 2028 \\ \hline  & 200 m & \
\begin{tabular}{c} P = 60\% \\ Q = 70\% \\ \end{tabular} & 462 m\({}^{2}\) & 115 & 1.3 m/s & 19 March 2028 \\ \hline  & 400 m &
\begin{tabular}{c} P = 60\% \\ Q = 70\% \\ \end{tabular} & 462 m\({}^{2}\) & 52 & 1.3 m/s & 19 March 2028 \\ \hline \hline \end{tabular}
\end{table}
Table 2: Flight parameters used for analyzing UAV images.  
Figure 11 displays a graph of the theoretical and measured GSDs using the bar target. The GSDs of the FC 6520 and FC 6310 sensors differed by 18-35% from the theoretical GSD. The GSDs of the iXM-100, a6000, and UltraCAM Eagle M2 sensors, however, only differed slightly, by 0-5%, from their theoretical values. These results suggest that the FC 6520 and FC 6310 sensors were more affected than the other sensors by the factors that reduced the image quality during UAV image capturing. Hence, sensors that differed considerably from the theoretical GSD should be avoided or carefully tested.  
Figure 10 is a graph of the GSD results analyzed using bar targets for flight height. For FC 6310 sensors, the GSDs were 3.4 cm (80 m in height), 4.0 cm (100 m in height), and 5.0 cm (150 m in height) as the flight height increased, resulting in poor image quality. The GSDs for iXM-100 sensors decreased to 1.6 cm (150 m in height), 2.2 cm (200 m in height), and 4.5 cm (400 m in height) as the flight height increased. In addition, the GSD for the iXM-100 sensors, which showed the best performance at the same flight height of 150 m, was the best, with a value of 1.6 cm. Subsequently, the GSD values were 3.1 cm for the a6000 sensor, 4.1 cm for the FC 6520 sensor, and 5.0 cm for the FC 6310 sensor.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Camera Model** & **Flight Height** & **Bar Target** & **Theoretical GSD** & **Measured GSD** \\ \hline a6000 & 150 m & 3.0 cm & 3.1 cm \\ FC 6520 & 150 m & 3.3 cm & 4.1 cm \\  & 80 m & 2.2 cm & 3.4 cm \\ FC 6310 & 100 m & 2.7 cm & 4.0 cm \\  & 150 m & 4.1 cm & 5.0 cm \\  & 150 m & 1.6 cm & 1.6 cm \\  & 150 m & 2.1 cm & 2.2 cm \\  & 400 m & 4.3 cm & 4.5 cm \\ UltraCAM Eagle M2 & 1000 m & 6.6 cm & 6.8 cm \\ \hline \hline \end{tabular}
\end{table}
Table 3: GSD analysis results using bar target.  
Figure 11: Comparison between the theoretical GSD and measured GSD using bar target.  
Figure 10: Comparison of the ground sample distance (GSD) analysis results obtained using the bar target.