## 4 Results and Discussion
### Discussion  
In Section 4.1, it could be seen that the IT2 FISs generated by gradually increasing the FOU size over a number of steps from \"\(\pm\)0%\" to \"\(\pm\)50%\" were able to compute \(R_{c}\) as linear-type and non-linear-type.  
Figure 16: Non-linear \(R_{c}\) by time and relative distance.  
\begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline \multirow{2}{*}{**Time (s)**} & \multirow{2}{*}{
\begin{tabular}{c} **Relative Distance** \\ **(nm)** \\ \end{tabular} } & \multirow{2}{*}{\(D_{CPA}\)/L} & \multirow{2}{*}{\(T_{CPA}\)/(L/V)} & \multicolumn{4}{c}{\(R_{c}\) Computed by FOU Size} \\ \cline{5-8}  & & & & \(\pm\)25\% & \(\pm\)30\% & \(\pm\)35\% &  
In addition, they gave the collision avoidance alarm depending on the give-way vessel in accordance with the COLREGs [2]. In this section, the measured linear and non-linear \(R_{c}\) according to numerical changing of input parameters, are discussed, as well as comparison with the existing FIS [16; 17] as presented in Figure 17, which is a numerical simulation result conducted in a state of Section 4.1.  
In terms of the measured linear and non-linear \(R_{c}\), though a total of the measured \(R_{c}\) should be gradually increased according to a reduction of both inputs \(D_{CPA}\)/\(L\) and \(T_{CPA}\)/(\(I\)/\(V\)), the FOU size \"\(\pm\)25%, \(\pm\)30%, \(\pm\)35%, \(\pm\)40%, and \(\pm\)45%\" computed repeated increase and decrease \(R_{c}\) in encounter situation between the OS and the TS. Accordingly, it is expected to be difficult that navigators make a decision for collision avoidance. On the other hand, as for the \(R_{c}\) measured by the FOU size \"\(\pm\)0%, \(\pm\)5%, \(\pm\)10%, \(\pm\)15%, \(\pm\)20%, and \(\pm\)50%\", state of repeated increase and decrease \(R_{c}\) did not exist in. Likewise, the existing FIS [16; 17] did also not compute \(R_{c}\) in a state of repeated increase and decrease. Nonetheless, the FOU size \"\(\pm\)0%, \(\pm\)10%, \(\pm\)15%, \(\pm\)20%, and \(\pm\)50%\" and the existing FIS [16; 17] computed identical \(R_{c}\) according to changing \(D_{CPA}\)/\(L\) and \(T_{CPA}\)/(\(I\)/\(V\)). However, the \(R_{c}\) computed by the FOU size \"\(\pm\)50%\" only was various according to changing parameters.  
According to rule 8 and 16 in COLREGs, the give-way vessel needs to take early action for collision avoidance. Accordingly, ship using the IT2 FIS based on FOU size \"\(\pm\)0%, \(\pm\)5%, \(\pm\)10%, \(\pm\)15%, \(\pm\)20%, and \(\pm\)50%\" could be possible that they early detect the collision risk faster than the IT2 FIS based on the FOU size \"\(\pm\)25%, \(\pm\)30%, \(\pm\)35%, \(\pm\)40%, and \(\pm\)45%\" and the existing FIS [16; 17]. At this time, a point of time for a give-way vessel using the existing FIS is 0.60, on the other hand, IT2 FISs generated by gradually increasing the FOU size over a number of steps from \"\(\pm\)0%\" to \"\(\pm\)50%\" is 0.33 due to extension of the T1 FIS-NC.  
For this reason, a ship using the IT2 FIS based on the FOU size \"\(\pm\)5%\" would be able to take early action for collision avoidance at an appropriate point of positioning and timing via various measured linear \(R_{c}\) according to changing of input parameters.