## 2 Data and Methodology
### Data Extraction and Exclusion Criteria  
The process of preparing the dataset comprised three distinct stages. First and foremost, the initial step (Stage 1) involved the formulation of a well-defined search strategy and the acquisition of relevant data. Subsequently, the acquired dataset underwent an initial screening (Stage 2) before proceeding to the final stage (Stage 3), where two distinct methods were employed for data refinement. The complete process of determining the dataset was visually depicted in Figure 3 and was elaborated upon in subsequent sections of this part.  
In the first stage of dataset compilation, a meticulously crafted search query was employed to gather the initial collection of documents. The query was solidly found in 2 themes: USVs and new technology. So that more insights into frontier developments would be taken, the choice of WoS as the primary data source was grounded in its recognition as a comprehensive and widely accepted repository of abstracts and citations from high-impact scientific publications [41]. The documents were sourced from the principal WoS Core Collections, namely the Science Citation Index Expanded (SCI-EXPANDED) and the Social Sciences Citation Index (SSCI).  
Figure 3: The process of determining the final data sample.  
Figure 2: Flowchart for the methods applied in this research.  
As for the design of the search query, a methodology of vocabulary iteration was utilized to add more synonyms. For instance, the abbreviation of _USV_ could be also interpreted as the _unmanned surface vessel_, _unmanned surface vehicle_, _autonomous surface vessel_, _automatic surface vessel_, _et al._ The main key 10 steps of query are shown in the Appendix A Table 11.  
Furthermore, the field of USVs has likely seen rapid growth and evolution in the past two decades. The 2000s onwards was a period where significant regulatory and industry changes occurred, impacting USV deployment and integration into various sectors. Reviewing the literature from this period allowed us to track these changes and their implications. Hence, the timespan was restricted to a period from 2000 to 2023 to support the novelty. In this paper, documents preceding 2 November 2023 were obtained and downloaded.  
The second phase of data selection entailed a rigorous evaluation of the documents obtained from WoS. This evaluation was primarily centered on scrutinizing the document titles, abstracts and associated keywords, including both Author Keywords and Keywords Plus, as the search query was accordingly updated over and over again until it had been searched for throughout the database. Documents meeting the initial validation criteria were identified as relevant and were earmarked for further analysis. The iteration of the search query is shown in the Appendix A. These qualified papers were included in the new dataset and were forwarded to the next step of filtering and determining the final sample (1025 papers).  
Thence, during the third stage of dataset preparation, all documents underwent a thorough manual scrutiny to assess the content and title against the predetermined criteria by excluding unrelated documents. Papers meeting these criteria were then categorized into the final group, and, eventually, 402 scientific documents were included in the final data sample. The documents contained 225 articles, 170 proceeding papers and 7 review articles. The final data sample would be applied in bibliometric analysis.