# A Survey on Unmanned Surface Vehicles for Disaster Robotics: Main Challenges and Directions
## 6 Discussion
### Technological Guidelines  
This section presents and discusses other technological (hardware and software) recommendations and guidelines for USV research focusing on Disaster Robotics. _Connectivity:_ Communication is fundamental for the operation and to guarantee that relevant sensor data reaches the operation center on land [229]. Still, communication problems with USVs often occur, since connectivity depends on the environment, weather, and wave conditions. Furthermore, the availability of broadband connectivity is limited in remote areas of the ocean [230] where only satellite communications with limited bandwidth are available. Even in shallow water and obstructed regions, in situations which cannot be handled by the USV alone (e.g., undetected imminent collisions), communication issues can be the difference between saving or destroying the USV, since the operator will not be able to intervene, jeopardizing the integrity of the USV and others. Therefore, communication problems must not be underestimated. Robust delay-tolerant protocols and equipment should always be considered for DM missions. However, as the human interaction with the USV increases, the bandwidth requirements also must increase to provide real-time video and responsive control, among other bandwidth demanding requirements involving USV sensors data [231]. Finally, in disaster scenarios where the fixed infrastructure may be compromised, IEEE 802.11 and satellites may be the best options to implement emergency communications for first-responders and victims. _Localization:_ Bad weather, being near the coast or man-made buildings (e.g., below bridges or next to dams) are all situations where localization problems related to poor GPS signal may occur. Therefore, localization strategies should be versatile in case of GPS problems. _Situational Awareness:_ In disaster sites, one of the primary functions of USVs' sensors is to provide information about its surroundings to operators [232; 233]. For USVs, it may involve the use of \(360^{\circ}\) cameras, effective underwater and out of water mapping sensors, microphones, and speakers. Such features will be helpful for several operations, including SAR, and detection of hazards in the surroundings of USVs. _Information Sharing:_ The operator must not be the only person with access to real-time information from the USV, including cameras. Information access to responders and experts must be straightforward. Enough bandwidth and an adequate user interface are required to allow multiple simultaneous users. _DM Fleet:_ A fleet of USVs offers advantages over a single USV including configuration flexibility, redundancy, coverage and throughput [234; 235; 236]. Furthermore, USVs and UUVs are complementary, and their combination can be beneficial for DM. For instance, disaster damage to man-made structures may be above and below the water level and sometimes only accessible with UUVs--e.g., oil spills and bridge inspection. UUVs can take advantage of USV localization and underwater mapping information [237], communications as well as communication capacity. Finally, UAVs can offer a view from the disaster site which is not possible for USVs [61; 79; 211], paramount for detecting victims [216] or hazards through an upper field of view. _Docking and Towing Capabilities:_ An asset for missions involving heterogeneous marine vehicles is enabling a USV to launch, recovery & docking for UUVs, UAV, or even other USVs. For example, [PERSON] et al. [73] uses a USV to carry a UAV into the complex stricken area. Then, while the USV approaches the affected area, the UAV takes off from the USV and sends global information about the environment. This way, it is also possible to rapidly carry UUVs to disaster sites and perform underwater tasks as needed. Similarly, USV towing capabilities could be used to tow containment booms [124; 125] or vessels in distress [238; 239] to help contain further environmental disasters (e.g., oil spills or ship sink) in case of maritime accidents [240].