## 3 Methodology
### Selection Criteria  
In order to select the appropriate papers to address the questions and contribute to the objective, inclusion and exclusion criteria were established for the documents to be reviewed. The main inclusion criterion pertains to academic documents (journal papers, book chapters, and conference papers).  
Two main approaches were considered for defining the inclusion/exclusion criteria: classification based on hull length and the primary architecture components required for autonomy and the USV application. The distinction criterion between small craft and larger vessels/ships is primarily based on the length of hull (LH), as established by the ISO 8666 standard [16]. This standard defines small craft as those with a hull length not exceeding 24 m. Consequently, if a craft exceeds this measurement, it is considered a vessel or ship, according to its length. Through this differentiation, applicable regulations, safety requirements, and technical specifications that various vessels must comply with are determined. In most cases, information regarding hull length is unavailable, and the identified studies are considered consistent with the context of small craft based on the search criteria.  
To establish the components of interest, we relied on the architecture description presented in [17], as shown in Figure 2. The guidance, navigation, and control (GNC) subsystem is a critical component for autonomous maritime vehicles [8; 9]. Moreover, the specific application of a USV is heavily influenced by the modules and equipment used for data acquisition in a given environment, upon which various types of studies are conducted or specific sector-based problems are solved. In this regard, the GNC subsystem  
\begin{table}
\begin{tabular}{c c} \hline \hline
**Database** & **Algorithm Search** \\ \hline \multirow{7}{*}{Scopus} & ( TITLE-ABS-KEY ( “boats” OR “boat” OR “small boats” OR “irverbotat” OR “small boat” OR “small boat” OR “small craft” ) AND TITLE-ABS-KEY ( “Unmanned Surface Vehicles” OR “Unmanned Surface Vehicle” OR “Autonomous Surface Vehicles” OR “Unmanned Surface Credit” OR “Unmanned Maritime Vehicle” OR “Remotely Operated Surface Vehicles” OR “Unmanned Surface Vessels” OR “USV” ) \\ \hline \multirow{7}{*}{WOS} & “boats” OR “boat” OR “small boats” OR “rivercat” OR “small boat” OR “small craft” (All Fields) and “Unmanned Surface Vehicles” OR “Unmanned Surface Vehicle” OR “Unmanned Surface Vehicle” OR “Unmanned Surface Vehicle” OR “Unmanned Surface Vehicles” OR “Unmanned Surface Vessels” OR “USV” (All Fields) \\ \hline \hline \end{tabular}
\end{table}
Table 4: Database search equations.  
\begin{table}
\begin{tabular}{c c} \hline \hline
**Data Source** & **Number of Papers** \\ \hline Scopus & 377 \\ Web of Science & 85 \\ \hline Total after duplicates removing & 387 \\ \hline \hline \end{tabular}
\end{table}
Table 5: Number of papers found in the databases with the equation “group 1 AND group 2”.  
and data acquisition are considered the key components for this study on the evolution of USV development.  
Given the aforementioned considerations, the following exclusion criteria were applied according to the corresponding stage of the methodology:  
* Identification: duplicate records.
* Screening: literature reviews, conference reviews, short surveys and weekly magazines.
* Eligibility: items with the following conditions.
* Labeled for the design of USV, hull, propulsion or power supply.
* Works in the field of major vessels.
* Conference or journal papers that are published in other conference or journal with updated or extended versions.
* Items that do not address the focus of the study or do not provide relevant information. This criterion includes works in the preconceptual phase with no clear indication of technological maturity level scaling.