## 1 Introduction  
In our paper, we focused on the development of a high-precision measurement system that would allow us to identify the area of maximum intensity of the electromagnetic field generated by the emitter coil in the hemispherical space limited by the ferrite plate in a WPT inductive system. Of course, other methods of increasing the PTE (power transfer efficiency) have appeared in the literature [1; 2]. A very widespread and applicable method is the insertion of metamaterials (MTMs) between the Tx and Rx coils [3]. In contrast to this, we sought a concentration of the field lines resulting from the WPT geometry and not a redirection of the field lines using artificially designed metamaterials, as in the abovementioned articles. The authors of [4] contributed concrete information for those needing to carry out field measurements using three-axis coil probes and those engaged in measurement setup development. This study highlighted the errors that may occur by measuring magnetic fields using coil-based sensors if the field volume exceeds the size of three-axis coil probes/transducers and analyzed the sensitivity to relative source orientation. Based on several investigations, the authors certified that the outlined methods could also be adapted to quantify proximity errors within the three-axis coil probe during measurement procedures for other field source topologies. We used a three-axis orthogonal sensor coil, but for a field generated by a WPT emitting coil rather than by a long line. The EN 61786-1 standard [5] provides guidance for the technical infrastructure used to measure the intensity of magnetic and electric fields up to 100 kHz. According to Part 1 of the abovementioned standard, which deals with measuring instruments, and Part 2, which deals with measurement procedures, three-axis coil probes, such as our 3D transducer, are recommended as common transducers. The standard presented in [6] confirms that an isotropic field sensor can be designed using three orthogonal coils, which are distributed so that the measured field is similar to the field in the middle of a sphere enclosing the three orthogonal coils. In the current paper, we followed these basic measurement principles, reproduced in worldwide accepted publications such as [5; 6; 7]. In agreement with the abovementioned research, it was confirmed that, in any case, the angular compensation of the yaw, pitch, and roll are entirely necessary. Our method of measuring the angular deviations of the sensor coil axis did not use Helmholtz coils, as in [7], but relied on the precise and stable positioning of the sensor in the proximity of the WPT emitter coil. For the total control--direction and intensity--of the EMF, it is necessary to assure the constant excitation of the coil. Because this cannot be guaranteed for the entire duration of the scanning process, it is necessary to apply a correction procedure. In [8], a calibration method was proposed using a distinct sensor placed in a fixed position, and the field intensity measured by this approach was used for the correction. In our study, we used the measured voltage at the emitter coil terminals as the reference signal. The spatial field distribution is of interest not only in the case of WPT, but also for investigating the EMC of a DUT. This prompted researchers to use an automatic systems to guide the movement of the measuring probe in the space of interest. For this reason, in [9], the proposal was to mount the probe on a mechanical arm with an electronic module that allowed 3D movements in space and the interpretation of the measured data according to the location. The solution for the WPT field proposed herein is like that presented in [9], with the particularity that it covers a significantly larger space, and the information obtained allows the detection of not only the field intensity, but also the spatial distribution of the field lines.