# Sensing in Inland Waters to Promote Safe Navigation: A Case Study in the Aveiro's Lagoon
## 3 Low-Cost Maritime Data-Sharing System Design and Evaluation
### System's User Interface (UI)  
This section explores the crucial phase of designing and validating the UI elements. An effective UI design that aligns with users' needs is essential for enhancing the user's experience and interactions with the system [75; 76]. This is particularly important in maritime contexts, where visual clarity and usability are vital to supporting maritime safety, especially during decision-making and risk communication processes. The maritime sailing environment (e.g., direct sunlight) can lead to Situational Visual Impairment (SVI), so it is essential to validate interfaces and functional requirements with the mariners who will be using them. Gathering feedback from those involved in maritime activities ensures that systems are aligned with user needs. Addressing SVI is critical in maritime operations where environmental factors affect visual perception and information processing [77; 78]. Therefore, a set of colors were observed and assessed under direct sunlight (Figures 2 and 3). To evaluate the system's final performance, an iPhone SE 2020 [79] with 625 nits was used. The evaluation showed that navy/dark blue and orange are the most legible colors in outdoor environments, making them ideal to be as the primary colors for the UI. In addition, the typography should be in the darkest shades possible to create a strong contrast and make the text legible, ensuring access to key actions within the UI while navigating in all maritime conditions. Figure 2: Outdoor color palette validation: (**a**) direct sunlight exposure on the screen during testing; (**b**) the set of colors chosen for evaluation. With the color palette and benchmarking analysis in place, it was easier to conceptualize ideas for integration with existing data-sharing systems to design the most optimized UI solution. Solutions such as a Navionics Sonar Map, Sea.AI, OpenSeaMap, SailRacer, and Savvy Navvy [65; 66; 67; 80] aided in representing maritime data in a UI, particularly by using larger numbers and concise textual descriptions to indicate the type of data being presented. Furthermore, the Waze application [81], originally designed for road navigation, influenced the maritime data sharing UI design by introducing crucial features, such as user identification through customizable avatars, a directional arrow indicator for the user's vehicle, a hazard button for reporting traffic or road hazards, and summarized data about road navigation. The interface was developed to be able to synthesize data received from the user's NMEA network (Figure 4). The user can choose whether to share these data with others (Figure 4-in Portuguese, \"_Partilhar dados_\"). The technical process of data sharing between vessels and how sensors contribute to this process can be better understood in the following section. Figure 4: The system shares real-time data, such as water depth, wind speed and direction, course, and speed over ground (SOC) with the community. Figure 3: UI with multicolored buttons evaluated in an outdoor context. Additionally, an emergency button was included to report incidents, such as shipwrecks, collisions, groundings, and men overboard. These reports are automatically displayed to all members using the data sharing system, similarly to Waze (Figure 5). The feature \"Sailors Around You\" (in Portuguese \"_Navegadores a minha volta_\") enables the users to monitor nearby boats identified by their avatar, boat name, and shared meteorological and oceanographic data, such as water depth and wind (Figure 6). Additionally, users can receive real-time tidal height information about any selected area by clicking on any given point in the main map (Figure 7). Figure 5: Meteo-oceanographic data-sharing system UI buttons. The orange button on the bottom represents the emergency button to report accidents and other complementary information to the maritime environment. Figure 6: Meteo-oceanographic data sharing system UI with two sections: data connected to the NMEA boat’s network and the information shared by users in the local area.