## 2 Materials and Methods
### Technical Design for AUV-Mounted Side-Scan Sonar Operations
#### 2.2.2 Equipment Inspection and Operational Execution  
A regular AUV system is equipped with various modules, including propulsion, power, communications, positioning, attitude, deployment, and recovery, each requiring thorough inspection. Initially, an overall inspection should be conducted before initiating the AUV. During this phase, the AUV should exhibit no visible damage, and the integrity of essential components such as propellers, rudders, and flotation materials must be verified, ensuring that backup components are readily available. Additionally, the internal pressure must exceed the maximum pressure expected at the most profound operational depth while maintaining stable pressure. Second, thoroughly examining the propulsion, power, and communications modules is necessary. This assessment involves using remote sensing techniques to adjust the speed and direction of the AUV's propellers and rudders, inflate the oil bladder, and move the sliders to test the three modules simultaneously. The remote-sensing part involves multiple communication methods, including radio, mobile communications, short-range Wi-Fi hotspots, satellite communications, and underwater acoustics. Third, the \begin{table}
\begin{tabular}{c c c} \hline \hline Installation angle of collision & & \\ avoidance device & Horizontal downward 45 \({}^{\circ}\) & \\ \hline Operating frequency of collision & & \\ avoidance device & & \\ \hline Collision avoidance response time & 1 s &
\begin{tabular}{c} Start responding after \\ 10 consecutive measurements \\ \end{tabular} \\ \hline Safe distance & 2 m & \\ \hline Response completion time & 0 s & Response and reverse loading \\ \hline AUV speed & 3 kn & \\ \hline \hline \end{tabular}
\end{table} 
Table 2: AUV assumed parameters. Figure 10: Schematic diagram of triggering alarm limits. positioning module is calibrated, with the DVL subjected to inspection after submersion and before decoupling. During the calibration process, which usually involves a stationary period of 10 min, the AUV needs to be rotated to assess the attitude module functionality. Fourth, verifying the full functionality of emergency recovery tools and auxiliary deployment and recovery mechanisms is essential when assessing the deployment and recovery module. Examining side-scan sonar payloads follows the inspection of the AUV's primary modules. First, it is essential to verify the integrity of the transducers on both exterior sides and ensure the functional connectivity of the cables. Second, upon submersion, the performance of several key aspects, which encompass verifying adjustments to the side-scan sonar's measuring range, assessing the interface between data logging and real-time data feedback, confirming the seamless connection of positioning and attitude information with side-scan sonar data, and evaluating the quality of the waterfall plot data for both port and starboard sides, across various frequency ranges must be observed. Also, a test should be conducted to determine if all relevant parameters are optimized to facilitate precise feature detection by the side-scan sonar. The emphasis of AUV operations lies primarily in the deployment and recovery of equipment and the ability to address potential operational disruptions. Due to increased collision risks during these phases, a stable vessel and optimal sea conditions are essential. Specifically, it is crucial to ensure that the swing angle of the mother vessel during deployment and recovery does not exceed 15\({}^{\circ}\) and that the sea state remains at or below Level 4, indicating moderate or calmer wind-wave conditions. In the event of an operational interruption, it is crucial to promptly receive notifications of the disruption, determine the equipment's surface location, and define the cause of the interruption to address the specific issue and assess the AUV's fitness for ongoing operations. This evaluation informs decisions regarding whether to resume operations or initiate recovery for maintenance.