# Methodology for Conceptual Navigational 3D Chart Assessment Based on Eye Tracking Measures
## 3 Results
### Map Indicators  
Taking into account the first conclusions drawn from the visual and survey assessments, further research focused on the development of an analytical method based on eye-tracking indicators. Due to the relatively large number of obtained indicators, we decided to examine the correlation among indicators W\({}_{1}\), W\({}_{2}\), W\({}_{3}\), and W\({}_{4}\) and, based on the results, reduce their number. Figure 15 presents the average quantity of correlations for the 2D and 3D maps. The average number of correlations refers to the mean count of correlation coefficients equal to or greater than 0.6 (considered a meaningful level of similarity, i.e., strong correlation), calculated among all pairs of cases within a given category. Correlations were computed separately for 2D and 3D map conditions, and the final value represents the average of these two results. Figure 16, on the other hand, shows the average correlation value for the 2D and 3D maps. The average correlation refers to the value of the correlation coefficients \(\geq\) 0.6, again calculated separately for 2D and 3D maps. Only correlations meeting or exceeding the 0.6 threshold were included in the calculation. The final result is the average of the mean correlation values for both map types. Figure 17 presents the results in the form of a matrix. Figure 17a shows the correlations of the readability indicators for the 2D map, while Figure 17b illustrates the correlations for the 3D map. \begin{table}
\begin{tabular}{p{113.8 pt} p{113.8 pt} p{113.8 pt} p{113.8 pt}} \hline
**Precision of Results** & **Interpretation of Results** & **Objectivity** & **Advantages and Disadvantages of the Method** \\ \hline
75\% of testers marked the map symbols were easy to find and interpret & High intensity of the symbols, giving a sense of clutter and confusion & Contours Wrecks Warline cable tracks Ferry routes & \multirow{2}{*}{Colour scheme} \\ \cline{1-1} \cline{3-3}
**Assessment of whether the 3D map correctly represented the  navigational situation** & **Evaluation of a 3D map visualisation for its effectiveness as a navigational aid** & **Personal perception of the need for this type of visualisation** & **Suggestions for improving the map symbols or map content** \\ \hline
63\% of testers (16 persons) marked YES 26\% of testers (8 persons) did not have absolute certainty & 14 testers marked as very important 3D ENC map as effective visualisation & More distinctive colour scheme Increased symbol-to -background contrast Map symbol scaling to avoid cluttering the image Improved 3D presentation of map symbols Map symbol design more in line with the IHO standard \\ \hline \end{tabular}
\end{table} 
Table 5: Cont. For both the 2D and 3D cases, the indicators \(W_{2}\) and \(W_{3}\) were significantly or strongly correlated with the other studied indicators (\(t\)-test for correlation significance was performed, where \(p<0.05\)). \(W_{2}\) had the highest average correlation > 0.6 and the highest correlation with the average number of saccades, average number of fixations, and time. Additionally, it was also the only W indicator of such a condition, together with Sm, Fm, T, and ID, between the 2D and 3D values (maps). Based on the obtained results, \(W_{2}\) was chosen for further analysis. \(W_{2}\) represents the light green regions of the heatmap, including the remaining ones (maximum defined area of the heatmaps). With this indicator, we were able to simplify, leaving behind more complicated analysis measures based on saccades and fixations. In addition to \(W_{2}\), the T indicator and the ID indicator were also presented as differential mean values for Formulas (8)-(10). The results obtained are shown in a box plot for the whole map series (Figure 18). Figure 16: Average correlations for 2D and 3D maps for a value greater than or equal to 0.6.