# Preliminary Results of an Astri/UWM EGNSS Receiver Antenna Calibration Facility
## 8 Full PCCs Validation  
The final step of Astiri/UWM result assessment is the consideration of the full PCC model and accuracy validation. Validation can be performed as previously described by checking the reproducibility of the obtained results, as well as by comparison to existing models (e.g., jigs14.atx). Figure 8 presents the differences between two independent calibrations carried out at an Astiri/UWM calibration facility. For the GPS L1 frequency, correction comparison was performed using the aforementioned approach proposed by [PERSON] and [PERSON] [30]. From the analysis of the internal accuracy of Astiri/UWM results for the full PCCs model, it can be confirmed that we have obtained consistent results. The differences do not exceed 2 mm over the whole antenna hemisphere, and this is valid for LEIAR10/NONE, as well as for TRM115000.00/NONE antenna. As for the elevation-only models, the most significant differences occur at low zenith angles (from 0\({}^{\circ}\) to 30\({}^{\circ}\)), which is mainly caused by the differences between the upward PCO components. In full dPCCs, severe observational conditions at low elevations are far more visible than those in elevation-only models. Note that low elevation angle signals have more noise, which is caused by crossing through an environment near the surface of Earth. In some horizontal directions and for high zenith angles (from 80\({}^{\circ}\) to 90\({}^{\circ}\)), the dPCCs obtained by comparison results of calibration one and calibration two exceed 2 mm. For the LEIAR10/NONE antenna, it is accurate in the west and east regions, and for the  
Figure 8: Differences between two independent calibrations of full PCCs for the GPS L1 frequency: (a) LEIAR10/NONE (left) antenna; (b) TRM115000.00/NONE (right) antenna. Figure 7: Zenith-dependent PCVs of the GPS L1 frequency: (a) LEIAR10/NONE antenna; (b) TRM115000.00/NONE antenna. TRM115000.00/NONE antenna, the most significant differences occur in the north-western and southeastern regions. Besides the internal repeatability of the experiment itself, external antenna calibration accuracy assessment with other calibration methods is mandatory. For this purpose, available IGS antenna files like igs05.atx, igs08.atx or igs14.atx may be used. These files contain most of the common geodetic absolute antenna datasets calibrated by the other international institutions or research groups. Although the igsxx.atx files contain so called \"mean-type\" models, they can be used as a good reference for comparison in case of the lack of an individual model. The first approximation of PCV is a mean-type PCC model. If more accurate data are needed for a specific antenna, individual calibration is inevitable [32]. For final external accuracy validation, the final model has been created for both antennas. The final models were created as based on the whole observational window (about five hours), covering three calibration sessions (as a mean result of three individual calibrations). In reference to the calibration values from igs14.atx, assessments similar to Table 2 were performed and are presented in Table 3 (using igs14.atx and Astri/UWM final PCCs models). The assessments in Table 3 demonstrate that the calibrated values for both antennas used in the experiments were estimated correctly and are comparable to IGS mean-type models from the igs14.atx file with an accuracy better than 0.6 mm for the horizontal component and better than 1.5 mm for the vertical component. Figure 9 presents the differences between IGS mean-type and Astri/UWM final full PCCs models. As previously, comparison was performed using the approach proposed by [PERSON] and [PERSON] [30]. When analyzing the external accuracy of the achieved results for the full PCC model, it can be seen that the results are slightly worse than in the case of internal accuracy, where the differences exceed 3 mm in some antenna hemisphere regions.