# Visual Navigation Systems for Maritime Smart Ships: A Survey
## 2 Smart Ships and Navigation Technology
### Smart Ships
#### 2.1.2 Progress and Development of Smart Ships  
Autonomous driving has long been utilized in many areas, and the question of autonomous driving in the shipping industry is no longer if it will happen, but when it will happen. The degree of autonomy has been categorized into three phases: In the first phase of autonomy, the crew, supported by the system, makes decisions from information or data collected during the operation of the ship. In the second stage, under the supervision and authorization of the crew, the ship can make decisions and initiate actions. And in the last stage, a fully smart ship can be realized [11]. Smart ships also have an impact on many aspects. The global maritime industry is characterized by rapid scientific and technological developments, and while manned and smart ships have some aspects in common, regulatory provisions should also take into account the characteristics of smart ships and develop specific regulatory policies. In addition, the most important thing to consider for smart ships is safety, and a range of technologies should be researched to control autonomous functions in order to improve safety. In terms of the industry, which has previously relied on the technology of the crew, autonomous technology will now re-invent the field of shipping by way of smart ships. More ship design and port facilities need to be considered to make smart ships efficient and reliable [7]. Intelligent ship autonomous technology is the integration of a variety of technologies, including autonomous navigation technology (navigation situational awareness, behavioral decision making and motion control), intelligent cabin operation and maintenance, communication technology, intelligent hulls, integrated experiments, etc. [12]. Intellectualization, greening and automation will become mainstream in global ship development. With the continuous improvement of ship intelligence, the development of unmanned cabin maintenance, assisted piloting technology and self-diagnosis of faults will all gradually reduce the labor demand of ships. In the future, the number of crew members with rich experience is likely to decrease, which will increase our concern for ship safety. The accuracy of driving-behavior decision making is directly related to the safety of water transportation, so the research on related decision-making algorithms is of great significance. The long-term navigation phase of smart ships requires comprehensive consideration of theoretical technology levels, unmanned ship navigation rules, human-machine cooperation, etc. Therefore, the study of human-machine interaction in smart ships is also a key area for the development of smart ships in the future. Human beings have advantages in understanding complex situations and reasoning, while machines have the advantages of high computational power and reliability in specific environments. Promoting the study of human-machine cooperation theories and technologies for ships can give full play to the advantages of human-machine cooperation and promote the prosperous development of smart ships. One aspect of the digital transformation of the shipping industry is the increasing digitization of shipboard systems, which is achieved by combining information technology with operating systems, and this high degree of interconnectivity and interdependence increases the likelihood of cyberattacks and cyber risks to a ship's digital infrastructure. Therefore, although the risk of cyberattacks can hardly be reduced to zero, it is necessary to study the related cyber decision making and the design of security architectures for ships. The most common propulsion systems used in modern ships are two-stroke diesel engines, steam and gas turbines, or combined marine propulsion systems, and these require the use of different fuels, lubricants, and so on. These complex systems require adequate personnel on board to monitor and maintain them.