An experimental study on the effect of antenna orientation on GNSS-IR

Abstract

Signal to noise ratio (SNR) data provided by the Global Navigation Satellite Systems (GNSS) receiver indicates the power of the received signal. Estimation of the quantities related to the reflection surface by analysis of the SNR data is called GNSS Interferometric Reflectometry (GNSS-IR). When a geodetic receiver is oriented to a direction, it receives stronger signals from the direction it is looking. In this study, two-day observations for a total of four days with zenith-looking (ZL) and horizon-looking (HL) receivers were performed. The data were analyzed comparatively in terms of amplitude and reflector height estimations. According to the reflector height estimations, it was seen that it is more appropriate to use HL receiver for elevation angles greater than 20°, while there is no significant difference from low elevation angles. Furthermore, since HL receivers receive reflected signals stronger than ZL receivers, the amplitudes of fluctuations in SNR data are found to be higher for HL receivers. Therefore, it can be said that it may be more appropriate to use HL receiver in GNSS-IR studies to determine quantities such as soil moisture to which SNR amplitude is sensitive.