## 1 Introduction
[9] compared the performance of a Huawei P10 + and an Ubblox NEO MST. In this case, the experimentation was conducted considering two different sites for the collection of the measurements and three different observation times (10, 30 and 60 min). The positioning modalities considered were static, kinematic and Single Point Position, and all results were obtained by fixing the ambiguities with the \"Fix and Hold\" method. [PERSON] and [PERSON] [10] discussed the quality of positioning, using a Huawei P30 (dual-frequency smartphone). In particular, the authors acquired several GNSS static survey sessions of 6-12 h for a total of about 80 h. The places chosen to acquire the experimentation, a roof and an open field, were all free from obstacles and elements capable of generating multipath effects. The Huawei P30 phase ambiguities could be corrected only for the observations in the GPS L1 carrier phase. The authors subdivided the observation data into sessions of shorter duration, 280 sessions of 5 min or 23 sessions of 60 min. After correcting the ambiguities, the errors in three-dimensional positioning (standard deviation) were approximately 0.04 m for the 5 min observations and 0.02 m for the 60 min observations; for observations lasting only a few minutes, ambiguity correction failed due to poor signal quality. [PERSON] et al. [11], through comparative experiments conducted on different smart devices, both in an outdoor environment and in an anechoic chamber, showed that it is possible to improve the GNSS measurements of Android devices by increasing the stability of the C/N0 signal-to-noise ratio and reducing the noise in pseudorange measurements. Furthermore, the authors point out how low-cost hardware components can influence the positioning errors of GNSS systems for smartphones. For example, [PERSON] and [PERSON] [12] found that the C/N0 of a smart device is 10 dB-Hz lower than that of a low-cost geodetic receiver characterised by rapid changes at high altitudes. The authors state that the smartphone GNSS receiver antenna was unable to mitigate the effects of multipath and had a non-uniform gain pattern: this was evidenced by replacing the device antenna with an external antenna. Therefore, the embedded antenna in smartphones is still a challenge in obtaining high accuracy positioning. [PERSON] and [PERSON] [13] studied the potential of Precise Point Positioning (PPP) with a dual-frequency smartphone, the Xiaomi Mi 8. The authors collected data from the smartphone and a Trimble R9 geodetic-quality GNSS receiver in PPP in both post-processing and real-time static and kinematic modes, demonstrating that decimetric-level accuracy in both post-processing and real-time modes, and metric accuracy in kinematic positioning mode, can be achieved with that smartphone. Recently, [PERSON] et al. [14] conducted extensive research on data from two Xiaomi Mi 8 s, two Xiaomi Mi 9 s, two Huawei P30 Pros, one Huawei P Smart, one Huawei P20, and two geodetic receivers (Topcon NetG5 and Trimble Alloy); the authors observed a decrease in the C/N0 of smartphones compared to geodetic receivers, noting that as the elevation of the tracked satellite increases, there is a corresponding increase in a divergence in C/N0 between smartphones and geodetic receivers. In this line of research, [PERSON] et al. [15] analysed the quality of the observations and evaluated the positioning performance in single-point positioning (SPP) with Code Pseudoranges of three smartphones: Huawei P30 pro, Xiaomi Mi 8 and Xiaomi Mi 9. The most accurate positioning in mono frequency (L1/E1/B1/G1) was obtained with the Huawei P30 Pro with a horizontal RMS of 3.24 m; Xiaomi Mi 8 and Xiaomi Mi 9 obtained RMS errors of 4.14 m and 4.90 m.  
The aim of this manuscript is to study the potential of GNSS positioning of smartphones by identifying the level of accuracy achievable with the use of a medium-cost device.