# Methodology for Conceptual Navigational 3D Chart Assessment Based on Eye Tracking Measures
## 1 Introduction
### Background and Aim of the Study
Only reliable products can ensure navigational safety. The reference data for determining the effectiveness of the new product in our research was a standardised 2D map. The focus was on the content of the navigation map and the selection of its most effective form without the need for testing in a fully operational environment. This approach enables different map concepts to be tested and the most effective one to be selected for further stages of research, i.e., Levels 2, 3, and 4. Such map testing was based on previous research with the ENC 3D concept map [58]. The main problem with 3D navigational chart testing is the large amount of work at the IT level that needs to be completed to prepare the test environment for an operational-like one. It is related to the development of symbols, interfaces, and the appropriate implementation of graphics libraries, such as Open GL or programming. An example of such a testing environment from previous research is presented in Figure 2. The proposed approach in the current work involves staging the testing, in which the first stage of testing may select a concept that has implementation potential, which justifies the later workload of developing test environments at subsequent levels (illustrated in Figure 1). In the adopted research option, our map testing concerns Level 1 aspects of ENC map visualisation using a GIS-based testing environment. The key question posed in the study was: how do we select the most effective map by testing different concepts? Based on this, the hypothesis was formulated that it is possible to develop a methodology for navigational map assessment--both standard 2D and conceptual 3D--to enable their comparison and selection for further research. In order to conduct this methodology, three evaluation criteria for navigational maps were chosen: the readability of the map, the correctness of object identification, and the time needed to identify map symbols. The main objective of this study was to develop a methodology based on universal indicators for assessing the effectiveness of maps using eye-tracking measurements. Traditional measures, such as the number of fixations, dwell time, or time to first fixation, are often analysed separately and are strongly dependent on specific tasks or experiment conditions, which can hinder their comparability across different map designs. The proposed indicator addresses this limitation by aggregating multiple eye-tracking parameters into a unified measure, thus enabling a more consistent evaluation of the concept map at an early design stage. Specifically, we integrated standard quantitative metrics, including the mean number of saccades, mean saccade duration, mean number of fixations and mean fixation duration,  
Figure 2: Exemplary concept 3D ENC in testing environment [58]. into the heatmap analysis. The aim was to explore the correlations among these measures and identify those most strongly related to the distribution of users' visual attention. This approach aimed to simplify the overall evaluation process by reducing the number of variables needed to assess the effectiveness of the map. Importantly, the research also involved developing a method for testing a series of navigation scenarios. Because navigational charts are used in a dynamically changing environment while the ship is in motion, assessing their effectiveness introduces additional complexity that is rarely considered in traditional mapping studies. This dynamic context of use necessitated the development of sequential map scenarios that better reflect actual navigation processes, in our case, at Level 1 ENC visualisation mode. To support the development and evaluation of the new indicator, the study was structured around three specific research objectives. Firstly, we conducted a visual analysis of eye-tracking indices obtained from user interaction with a set of test map scenarios. Secondly, we analysed responses from a user survey that included both traditional 2D electronic navigation maps (ENCs) and proposed 3D visualisations.