## 3 Autonomous Vehicles and Monitoring Platforms
\begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline  & & **Operates** & & \multicolumn{2}{c}{**Controlled by**} & \multicolumn{2}{c}{**Navigation System**} & \multicolumn{2}{c}{**Propulsion**} \\ \hline
**UMV** & **In Air** & \begin{tabular}{c} **Water** \\ **Surface** \\ \end{tabular} & \begin{tabular}{c} **Under** \\ **Water** \\ \end{tabular} & **Operator** & **Independent** & \begin{tabular}{c} **GPS** \\ **Navigation** \\ \end{tabular} & \
\begin{tabular}{c} **\(e\)-** \\ **Compass** \\ \end{tabular} & **Propellers** &
\begin{tabular}{c} **Variable** \\ **Buoyancy** \\ \end{tabular} \\ \hline UAS & X & & & X & X & & X & & X \\ ASV/USV & & X & & X & X & & X & \\ AUV & & & X & X & & X & \\ ROUV & & & X & X & & X & \\ Glider & X & X & X & & X & X & & X \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Features of unmanned vehicles (UMVs) classified according to the types (unmanned aerial system (UAS), autonomous surface vehicle or unmanned surface vessel (ASV/USV), autonomous underwater vessel (AUV), remotely operated underwater vessel (ROUV), and gliders). The main features are indicated in terms of environment explored, control, navigation system, and propulsion type. recent advances in the field of smart tools compared with ROUVs, which were introduced several decades ago and have been improved in terms of efficiency and cost in the last few years. Additional equipment is commonly added to expand the vehicle's capabilities. These may include sonars, magnetometers, a still camera, a manipulator or cutting arm, water samplers, and instruments that measure the water clarity, water temperature, water density, sound velocity, light penetration, and temperature [57]. ASVs and AUVs suitable for marine monitoring can vary from relatively small vehicles lifted by one or two persons and deployed from a small inflatable boat to large diesel-powered surface vessels [58]. In particular, smaller vessels are able to operate with a high level of autonomy and are also capable of staying at sea for several months. In contrast, larger surface vehicles often tend to be more tightly controlled. Surface vehicles have the advantage of being able to continuously receive GPS position data while navigating, and their locations can be accurately recorded at all times. Subsurface vehicles do not receive GPS data while they are immersed and therefore must generally rely on depth measurements and dead reckoning using electronic compasses [59; 60]. Moreover, ASVs can operate safely in hazardous locations and at night and can cover much larger areas, mitigating the risk of crew fatigue. In some cases, they can independently operate off large ships [61]. ASVs started to be developed at an academic level in 1993, when the MIT presented its first vessel, called ARTEMIS [62; 63]. The newer ASV, called the Shallow Water Autonomous Multipurpose Platform (SWAMP), is a full-electric catamaran built with the purpose of being a modular multi-functional vehicle, having several applications for a range of missions, such as geomorphological analysis, water sampling, and physical and chemical data collection in harsh environments [64]. This vehicle has four thrusters, azimuth pump-jet thrusters that are flush with the hull, small-draft soft foam, an unsinkable hull structure with high modularity, and a flexible hardware and software architecture [64]. Generally, USVs are associated with unmanned surface vehicles (USVs) [65]. Usually, USVs are equipped with a central processing unit and different memories for saving and providing a preliminary management of the acquired data (e.g., compression and classification). In addition, batteries and photovoltaic panels are equipped to increase the electrical autonomy as much as possible, which generally turns out to be one of the major limiting factors [60]. ENDURUNS is an example of a system that integrates both an AUV and an USV system. The USV is equipped to support the power requests of both systems with photovoltaic panels and rechargeable battery packs.