# Early Results on GNSS Receiver Antenna Calibration System Development +
## 4 Conclusions  
The new GNSS receiver antenna calibration system developed at the Laboratory for Measurements and Measuring Technique (LMMT) of the Faculty of Geodesy of the University of Zagreb in Croatia can provide meaningful antenna calibration results for the GPS L1 frequency. According to the obtained experimental research results regarding the Trimble Zephyr 2 Geodetic antenna, an estimated agreement within 0.52 mm, in terms of RMS, with the accredited Geo++ GmbH results, was achieved. Therefore, our calibration results also confirm the compatibility of LMMT GPS L1 calibrations with the IGS accredited Geo++ GmbH calibrations.  
Conceptualization, A.T., M.Z., M.S. and D.B.; methodology, A.T., M.Z. and M.S.; software, A.T.; validation, A.T. and M.Z.; formal analysis, A.T. and M.Z.; investigation, A.T.; resources, A.T. and M.Z.; data curation, A.T.; writing--original draft preparation, A.T.; writing--review and editing, M.Z., M.S. and D.B.; visualization, A.T.; supervision, M.Z.; project administration, A.T.; funding acquisition, M.Z. All authors have read and agreed to the published version of the manuscript.  
\begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline  & \multicolumn{4}{c}{**Full Antenna Hemisphere**} & \multicolumn{4}{c}{**Reduced Antenna Hemisphere**} \\  & \multicolumn{4}{c}{**(0\({}^{\circ}\) Elevation Cut-Off)**} & \multicolumn{4}{c}{**(10\({}^{\circ}\) Elevation Cut-Off)**} \\ \hline
**Min.** & **Max.** & **RMS** & **Range** & **IQR** & **Min.** & **Max.** & **RMS** & **Range** & **IQR** \\ \hline –2.92 & 0.72 & 0.52 & 3.64 & 0.44 & –1.64 & 0.72 & 0.34 & 2.36 & 0.41 \\ \hline \hline \end{tabular}
\end{table}
Table 2: Quantitative measures of the difference between Geo++ GmbH’s and LMMT’s individual absolute calibrations: minimum, maximum, root-mean-square (RMS) deviation, range, and interquartile range of \(\Delta\)_PCC_. All values are in millimeters (mm).  
Figure 5: Geo++ GmbH and LMMT PCC differences (\(\Delta\)_PCC_) of antenna TRM57971.00 NONE (S/N: 30739001) for GPS L1 (G01) frequency after transformation to common PCO and datum.  
**Funding:** This research was funded by the University of Zagreb under the research project \"Automatization of measurement procedure in the Laboratory for Measurements and Measuring Technique of the Faculty of Geodesy\".  
**Institutional Review Board Statement:** Not applicable.  
**Informed Consent Statement:** Not applicable.  
**Data Availability Statement:** The data presented in this study are available on request from the corresponding author.  
**Acknowledgments:** The authors would like to express their gratitude to the following: the Inea Group, the local Mitsubishi Electric authorized distributor, for great support regarding robotic automatization; the State Geodetic Administration of the Republic of Croatia for providing the GNSS equipment used for this research; [PERSON] of Geomatika-Smolcak Ltd. for his many useful receiver-specific advices; [PERSON] for his technical and logistical assistance during calibration field activities; and [PERSON] for his help during the production of antenna-robot mounting elements.  
**Conflicts of Interest:** The authors declare no conflict of interest.