## 4 Conclusions  
This work enabled the determination of the positioning accuracy of the used GNSS receivers, with different technical characteristics and working modes, during dynamic tests. Moreover, it was possible to determine the influence of the external antenna and RTK differential correction technique on the positioning accuracy achieved by using these satellite receivers. The results showed that the external antenna was able to correct the positioning error. RTK differential correction technique was shown to be fundamental for achieving more accurate position data. The effect of differential correction was shown to be significant on the improvement of the positioning accuracy achieved by using the GNSS receivers Stonex S7-G and S5. All the satellite receivers tested together with the external antenna (Stonex S7-G, Stonex S5 and Thales MobileMapper Pro) showed an improvement of positioning accuracy. The effect of the external antenna was significant on the improvement of the accuracy achieved by using, above all, the GNSS receiver Stonex S5. The satellite receiver Thales MobileMapper Pro showed the worst positioning accuracy. The low-cost receiver Quanum GPS Logger V2 surprisingly showed a mean positioning error of only 0.550 m. The positioning accuracy of the above receiver was slightly worse than that achieved by using Stonex S7-G without the external antenna and differential correction. However, this accuracy was even better than that recorded by using Stonex S5 without differential correction, both with and without the external antenna. From the results of this work, it is possible to deduce that:  
* the GNSS receiver Stonex S7-G can be used together with an aided guidance system able to control a seed drill or a transplanter, in order to assure the correct offset between adjacent passes, without overlapping and failures, as confirmed in [29];
* the satellite receiver Stonex S5 can be used only for the geo-referenced measurement of within-field crop and soil parameters and spatially variable rate crop input application;
* the GNSS receiver Thales MobileMapper Pro can be used only for the geo-referenced measurement of within-field crop and soil parameters by using the differential correction in post-processing;
* the low-cost receiver Quanum GPS Logger V2 (U-Blox NEO-6M), assembled at SAAF Department of the University of Palermo, as a consequence of the achieved positioning accuracy, can be used for the geo-referenced measurement of within-field crop and soil parameters; moreover, at present, low-cost GNSS receivers can be mounted on UAVs (Unmanned Aerial Vehicle) and UGVs (Unmanned Ground Vehicle), for enabling an accurate real-time positioning and, therefore, promoting the use and development of these vehicles [12]. Further research is certainly needed to compare the accuracy of the tested receivers in less favourable conditions. Anyway, this study can contribute to improving farmers' perception and uptake of precision agriculture in order to increase the ca.1% of cultivated area where it is currently implemented in Italy. It is necessary to encourage farmers to invest in technology useful for their needs and also to use low-cost devices like those described in this paper. **Author Contributions:** Conceptualization, A.C., P.F. and S.O. ; methodology, P.C., A.C. and S.O. ; software, G.M., S.O. and E.R. ; validation, G.M. and S.O. ; formal analysis, S.O. and E.R. ; investigation, P.C., S.O. and E.R. ; resources, P.C. and S.O. ; data curation, G.M., S.O., E.R. and M.V. ; writing--original draft preparation, A.C., E.R. and M.V. ; writing--review and editing, A.C., P.F. and M.V. ; visualization, S.O. and E.R. ; supervision, P.F. All authors have read and agreed to the published version of the manuscript. **Funding:** This research received no external funding. **Acknowledgments:** The authors of this research acknowledge the informatics collaborator Mr. [PERSON], for assembling, at the SAAF Department, the used low-cost satellite receiver Quanum GPS Logger V2 (U-Blox NEO-6M) and participating in the tests.