# A Survey on Unmanned Surface Vehicles for Disaster Robotics: Main Challenges and Directions
## 5 USV Applications for Preventive Maintenance and Disaster Response
### Structure Inspection for Damage Assessment  
In the response phase, after a disaster has occurred, USVs can be used to perform damage assessment in buildings and infrastructure. The goals of this application are to perform structural inspection and evaluate the constructions' post-disaster structural integrity, identifying dangerous areas for response crew, as well as mapping debris and locating safe access routes to affected zones. However, few works have real-world deployment for this application, as it must take place after a disaster.  
The first known deployment of USVs for damage assessment was in 2005, three days after Hurricane Wilma's landfall [19; 62; 61; 63]. The Center for Robotic-Assisted SAR (CRASAR), along with the Institute for Safety Security Rescue Technology (iSSRT) used a USV and UAV team to assist response crews in verifying the structural integrity of Marco Island's seawall and piers, as well as to locate submerged debris and define safe lanes for sea navigation. In this deployment, the authors validated the suitability for USVs in DM, identified cooperative USV-UAV strategies (i.e., USVs may provide external view for situation awareness, spot areas to be inspected and serve as communication relays), and identified a UAV deployment pattern, where short and localized flights, made to take advantage of line-of-sight, are preferable over a single continuous fly-over.  
In 2008, CRASAR also assisted in the response phase of hurricane Ike [62; 63; 64], successfully deploying a Sea-RAI USV to inspect the structural integrity of the Rollover Pass Bridge in Texas, USA. The deployment missions were: (1) To evaluate the utility and performance of the USV in inspecting the bridge's submerged structure; (2) To map the hurricane's debris field. In the second mission, the Sea-RAI was deployed three times, using an acoustic camera to obtain images of the bridge substructure and debris surrounding its pliers--which were analyzed by the response crew to verify the bridge's structural integrity.  
The deployment team identified challenges in three areas: USV control and navigation, human-robot interaction, and data uncertainty. First, swift water currents limited the times and duration of the USV missions and required tethering of the USV. Operation near and under bridge also produced GPS loss and errors (1% away from the bridge and 22% near or under it), which required teleoperation of the Sea-RAI. Second, the deployment confirmed the need for multiple displays for different information and reinforced USV payload. As different specialists were involved in the disaster response team, not all information from the robot is useful for everyone, which calls for multiple customizable displays. In the broader context of human-robot interaction, the USV's payload must be robust to withstand the water force, as it knocked the acoustic camera out of alignment during operation, confusing the operators and leading to coordination challenges between team members. Finally, uncertainty in the data from the acoustic camera due to shadows and differing viewpoints presented challenges for the accurate understanding of submerged structures.