Retrieving the SNR metrics with different antenna configurations for GNSS-IR

Multipath, which is a major source of error for precise positioning, is the effect that occurs when Global Navigation Satellite Systems (GNSS) signals reach the receiver by reflecting from one or more surfaces. Reflected signals affect the signal-to-noise ratio (SNR) data provided by the receiver, indicating the signal strength. The structure of the antenna of the receiver and the direction in which it is oriented also change the strength of the received signal. In this study, the effect of antenna orientation and polarization on SNR data was demonstrated by using the method called GNSS-Interferometric Reflectometry (GNSS-IR), in terms of reflector height estimates. A geodetic GNSS receiver (CHC i50) and two different smartphones (Xiaomi Mi8 and Xiaomi Mi8 Lite) were used in the four-day experiments. The geodetic receiver was established as zenith-looking (ZL) in the first two days and as horizon-looking (HL) in the last two days. Smartphones were placed on the same mast with the HL receiver in the last two days. It was seen that it is more appropriate to use a 0°-60° satellite elevation angle range in the common use of all receivers’ data. In the 30°-60° range where the ZL installation receives the multipath signals weakly, it has been found that the HL receiver and smartphones have reflector height estimation accuracies with values ranging from 1.9 cm to 2.5 cm. In short, for different elevation angle ranges, accuracies below 2 cm could be obtained with each receiver. Thus, different antenna configurations may be used in GNSS-IR studies, depending on the characteristics of the study area and the surface feature to be determined.