# Evaluation of Low-Cost GNSS Receiver under Demanding Conditions in RTK Network Mode
## 5 Conclusions  
The u-blox ZED-F9P performs very well for a GNSS receiver in this price range. The ANN-MB-00 antenna is suitable for precise measurements and provides centimeter accuracy, but only in conditions with sufficient horizon exposure. The ZED-F9P configuration with the ANN-MB-00 antenna provides an excellent relation of positioning quality to price, as well as size, weight or power consumption. This makes the u-blox a very versatile receiver that can be used in many industries, such as autonomous vehicles, building monitoring, surveying, robotics and marine. The simple configuration of the u-blox C099-F9P application board and the management of the ZED-F9P via the u-center software supplied by the manufacturer provides the user with an accurate position just minutes after unpacking the device for the first time. Software libraries available on the Internet further assist in implementing the device in individual research and projects. Additionally, the manufacturer provides user support through reliable, comprehensive technical documentation, and many solved problems can also be found in online forums as the u-blox ZED-F9P becomes increasingly popular. In the case of positioning in more challenging conditions and/or with greater precision, a replacement for the ANN-MB-00 antenna with a model from another manufacturer of the survey-grade types would be worth considering. The Leica AS10 antenna has significantly improved the measurement performance of the u-blox ZED-F9P, with smaller PCVs (phase center variations) and more efficient multipath reduction. The u-blox ZED-F9P configuration with the Leica AS10 antenna turned out to be worse than the Leica GS18T professional geodetic receiver only in the last position, with better results on the previous positions. It can be assumed to be a promising outcome, considering the price gap between both devices. The u-blox receiver was the most disappointing on the last station--not because it could not measure as accurately as the Leica GS18T, but because it indicated a fixed solution that differed very much from the reference coordinates. This fact causes uncertainty when measuring with this receiver in conditions of insufficiently good visibility and satellite configuration or placement. The Leica GS18T, unlike the u-blox, either maintained accuracy and marked the measurement as fixed, or the solution status changed to float, and the user had no doubts about the quality of the measurement. The manufacturer of the ZED-F9P should apply additional filters that would more accurately help to remove the multipath effect. In addition, measurement confidence should be increased or the insufficient measurement confidence should be alerted. Figure 15: The MSD values [m] on each station point. Reference coordinates were determined with a precision of one order of magnitude higher than the one of RTK/RTN measurements. Measurement series were performed alternately to ensure that the satellite configuration was as similar as possible between measurements in successive hardware configurations. The measurement stations were placed in locations with increasingly difficult measurement conditions, as shown in Figure 15 by the increasing coordinate differences and variations in standard deviations. Therefore, it can be concluded that the tests were carried out reliably, as shown in the results above. In the subsequent tests, it is planned to check the positioning quality of the u-blox ZED-F9P receiver on the move to recognize even better its applicability in the automotive industry. Based on the measurement conditions of the above test, a suitable route will be proposed, as well as an appropriate quality reference positioning (robotic total station with the 360-degree prism, coaxially mounted with the ANN-MB-00 antenna, through a unique adapter made by 3D printing technology). Conceptualization, D.J. ; methodology, D.J. and P.K. ; software, D.J. ; validation, D.J. and P.K. ; formal analysis, D.J. and P.K. ; investigation, D.J. and P.K. ; resources, D.J. and P.K. ; data curation, D.J.