## 3 Models and Methods
### Compliance Assessment Procedure  
Several product assessment standards and technical reports define spatial averaging methods for exposure to nonuniform magnetic fields. The spatial averaging method involves averaging the magnetic field strength measured (computed) at specific spatial points. For instance, IEC TR 62905 [23] specified the measurement of magnetic fields on a plane located 20 cm from three points at different heights (0.5, 1, and 1.5 m) for humans standing by the side of the vehicle. This reference is derived from IEC 62110 [22]. IEC PAS 63184 [24] extended this by including the closest accessible point to the three points. IEC PAS 63184 also outlined the measurement of the magnetic field at the center position of the floor flat surface and the points at the center position of the headrest, backrest, and seat for sitting on the driver's seat. We outlined three definitions for each posture, as shown in Table 2 and Figure 4. In Definition 1 for outside the vehicle, the measurement point was defined at the heights of 0.5, 1.0, and 1.5 m from the ground based on IEC TR 62905. In Definition 1 for inside the vehicle, the measurement heights are 0.5, 1.0, and 1.2 m from the floor, corresponding to the cushion, chest, and head of the seat, respectively. In Definition 2, the closest accessible point was incorporated into Definition 1 based on IEC PAS 63184, considering the foot. In Definition 3, the measurement point was defined at the heights of the closest accessible point and two points, each 25 cm higher from it, aiming to be more stringent than Definitions 1 and 2. The measurement points of 0.35, 0.6, 1.0, and 1.2 were defined along a 15-degree angle of the seat to align with the central axis of the human body, considering the human body model sits in the driver's seat in a realistic posture. Using these definitions, we calculated the spatial average of the magnetic fields (\(H_{\text{ave}}\)) and compared them with the limit prescribed in the exposure guidelines [7; 9]. In this study, we compared the ratio of \(H_{\text{ave}}\) to RL (\(H_{\text{BL}}\)) and that of the maximum internal \begin{table}
\begin{tabular}{l c c} \hline \hline \multicolumn{1}{c}{**Definitions**} & \multicolumn{1}{c}{**Heights from The Ground [m]**} & \multicolumn{1}{c}{**Heights from The Floor [m]**} \\ \hline
1: TR 62905 & 0.5, 1.0, 1.5 & 0.5, 1.0, 1.2 \\
2: Maximum point + PAS 63184 & 0.06, 0.5, 1.0, 1.5 & 0.1, 0.5, 1.0, 1.2 \\
3: Every 25 cm from & 0.06, 0.31, 0.56 & 0.1, 0.35, 0.6 \\ maximum point & & \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Definition of the heights of magnetic field strength measurement used for averaging. Figure 4: Measurement points outlined in each definition for outside and inside the vehicle body (unit: m). electric field (\(E_{\rm max}\)) to BR (\(E_{\rm BR}\)). The spatial averaged method was evaluated using the following equation:  
\[a_{c}=\left(\frac{E_{\rm max}}{E_{\rm BR}}\right)\Big{/}\Big{(}\frac{H_{\rm ave} }{H_{\rm RL}}\Big{)} \tag{2}\]  
where \(a_{c}\) represents an index of the conformity ratio of external magnetic and internal electric fields to the guideline. If \(a_{c}\) is less than 1, it indicates that the assessment based on the spatial average of the magnetic field in the corresponding definition is more stringent than that based on the maximum electric field. The magnetic field strength was computed in the domain averaged over 100 cm\({}^{2}\), assuming the 100 cm\({}^{2}\) loop antenna prescribed in the IEC standard [44; 59]. This averaging area was considered as a postprocessing step for the computed field distribution. In the evaluation of the internal electric field in anatomical models, the skin-to-skin contact is not negligible [12], which is inherent to the discretization of a real human model into a finite-resolution model. This computational weakness results in a higher internal electric field at the corresponding part. Therefore, the electric field at skin-to-skin contact was excluded, as mentioned in IEEE C95.1 standard [12].