###### Abstract
For a low-cost receiver that relies on code observations, the positional error due to multipaths is very significant and can reach tens of metres [12; 13], and the GNSS receiver may even experience a loss of lock in the event of severe multipath conditions [14]. Real-time kinematic positioning, even for geodetic receivers, depends on the quality of code measurements to shrink the search space in resolving the carrier phase ambiguity [15]. In doing so, multipath-corrupted pseudorange measurements can increase the time needed for initialization. [PERSON] and [PERSON] [16] demonstrated, using simulated GPS observations, that multipaths can also cause spurious periodic signals at dracoinic harmonics on station coordinates. Consequently, the vertical component of the station coordinates is expected to result in erroneous tropospheric zenith delay estimates [16]. Time/frequency transfer between distant GNSS receiver clocks depends on code measurements, and the accuracy at a level of a few nanoseconds ultimately relies upon the quality of code measurements that is not adversely affected by code multipaths [17]. The multipath error also has a severe impact on the attitude determination of spacecraft where 90% of the carrier phase measurement's overall error budget is due to multipaths [18]. Commonly, a successful reduction (\"smoothing\") in pseudorange multipath depends on the exploitation of reduced multipath effects on carrier phase measurements. A multipath is generally understood to mean that the reflected signal comes from the far-field zone, employing the geometrical ray optics principle characterising the effects [8]. The geometrical ray optics consider that the GNSS signal is only composed of direct, reflected and refracted rays. In contrast, a GNSS antenna causes currents to be produced in near-field reflecting materials, and these currents may result in considerable coupling with the GNSS antenna. This, in turn, alters the amplitude and phase properties of the GNSS antenna in comparison to its original pattern, causing the antenna to become essentially \"uncalibrated\" [10]. Scattering located within the near-field of the antenna is more severe than far-field scattering [8]; often, the near-field region implies the first 50 cm surrounding the antenna phase centre [19]. Typically, the influence of multipath can be analysed by linear combinations of pseudorange and carrier phase measurements for various frequencies in GNSS observables. [PERSON] [20] used the parametrization of legacy GPS \(L_{1}\) and \(L_{2}\) frequencies and generated code multipaths, \(MP1\) and \(MP2\) metrics, respectively. However, reducing and even avoiding multipath error is much more complex. When multipaths exist, the best way to reduce the multipath effects (not in any particular order) is to install the GNSS antenna far away from potential reflecting surfaces in the antenna environment inside the Fresnel zones [21]. Normally, this is not always possible. Currently, the suppression or reduction of the multipath effect relies on an appropriately designed antenna (e.g., Choke Ring antenna ) by attenuating a GNSS signal entering the receiver [22; 23]. On the receiver side, using the receiver architecture (e.g., delay-lock loop techniques [24]) can partially avoid a multipath error. While not always applied, a large ground plane located beneath the antenna also helps in modifying the shape of the antenna's gain pattern so that it becomes insensitive to signals below and at lower elevation angles [15]. Furthermore, the GNSS antenna is designed to preferentially receive a right-hand circular polarised (RHCP) signal; therefore, the signals undergo reversal in handedness and become left-hand circularly polarized after reflecting from a nearby surface is selectively avoided.