# Floating Photovoltaic Plant Monitoring: A Review of Requirements and Feasible Technologies
## 5 Technologies for Autonomous Water Basin Mapping and Monitoring
### State of the Art of Surface and Underwater Robotic Systems  
There are actually mainly three types of autonomous drones that can be used in the FPV scenario. They are as follows:  
* ASVs (autonomous surface vehicles), also called USVs (unmanned surface vehicles), are boats controlled by an autopilot, commonly linked to a ground station through at least one radio trans-receiver (for sending telemetry data) and to a radio-controller through a radio receiver module aboard the vessel, enabling manual recovery of the ASV or failsafe functions at any time. Positions, trajectories, and all on-board data acquired aboard the vessel are available on the ground station (or directly in a control room), making it possible to set waypoints of interest and let the robot follow them automatically. * ROVs (Remotely Operating Vehicles), due to their cost-effectiveness, excellent maneuverability and on-line acquisition capability, represent the current commercial tool for widespread use in underwater exploration. Some ROVs configurations can be equipped with an extension module, enabling the tethered cable to supply the energy required for an indefinite time due to the availability of an electrical socket on the surface. * AUVs (Autonomous Underwater Vehicles), unlike ROVs, are characterized by the absence of a tethering cable, relying on a battery pack for power supply and off-line data acquisition capabilities. Indefinite operation requires permanent electrical recharge/docking/recovery stations. The cost of these vehicles increases with the number of sensors fitted on-board. The more automated and powerful the vehicle, the more complex the missions it can perform. All three systems can be broadly categorized into two groups: those still in the research stage and those that are already a market diffusion. Regarding the research stage of ASVs, the SeaTrac autonomous boat [110] is an example of advanced technology designed for surface monitoring, equipped with various sensors to collect environmental data. Autonomous boats like the Saildrone offer extended deployment times and are used for extensive data collection, capturing observations at the air/sea interface by solar-powered meteorological and oceanographic sensors [111]. The IntCatch project is also noteworthy [112]. Although at a lower technological maturity, ENEA's ASV shown in Figure 4 is another example of autonomous ASV prototype. Figure 4: Examples of ASV, ROV, and AUV. (**a**) The ENEA’s ASV prototype during a mission; (**b**) a commercial mini ROV for water quality monitoring [courtesy of Eurosportos srl—Chasing Innovation Idt]; (**c**) ExRay wireless ROV [courtesy of Hydromea SA—]; (**d**) Vertex AUV advanced prototype [courtesy of Hydromea SA—]; (**e**) ENEA’s AUV prototype VENUS; (**f**) Mesh Network. An ENEA theoretical depiction of a possible swarm communication link (multi-hop) between cooperative underwater drones. Industrialized ASVs from companies such as Liquid Robotics and ASV Global are designed for robust environmental monitoring and surface inspections. These commercial ASVs are widely utilized in marine research and environmental assessment. All ASVs, however, face challenges related to autonomy and energy management [113]. In most cases, PV modules on the vessel or wind-powered technology could resolve these issues. On the other hand, in the first group of underwater drones, Remotely Operated Vehicles such as the OpenROV and BlueROV2 offer real-time control and data transmission, making them versatile tools for detailed inspections [114]. The main challenge with ROVs is their tethered nature, which can limit operational range and cable deployment. Commercial ROVs from manufacturers such as VideoRay and Deep Trekker offer solutions for underwater inspection and maintenance, often used in aquaculture and offshore energy sectors. These tethered systems provide a real-time video feed and can be equipped with various sensors for water quality assessment and structural inspection.