Abstract
The access to Android-based Global Navigation Satellite Systems (GNSS) raw measurements has become a strong motivation to investigate the feasibility of smartphone-based positioning. Since the beginning of this research, the smartphone GNSS antenna has been recognized as one of the main limitations. Besides multipath (MP), the radiation pattern of the antenna is the main site-dependent error source of GNSS observations. An absolute antenna calibration has been performed for the dual-frequency Huawei Mate20X. Antenna phase center offset (PCO) and variations (PCV) have been estimated to correct for antenna impact on the L1 and L5 phase observations. Accordingly, we show the relevance of considering the individual PCO and PCV for the two frequencies. The PCV patterns indicate absolute values up to 2 cm and 4 cm for L1 and L5, respectively. The impact of antenna corrections has been assessed in different multipath environments using a high-accuracy positioning algorithm employing an undifferenced observation model and applying ambiguity resolution. Successful ambiguity resolution is shown for a smartphone placed in a low multipath environment on the ground of a soccer field. For a rooftop open-sky test case with large multipath, ambiguity resolution was successful in 19 out of 35 data sets. Overall, the antenna calibration is demonstrated being an asset for smartphone-based positioning with ambiguity resolution, showing cm-level 2D root mean square error (RMSE).
Highlights
The Global Navigation Satellite System (GNSS) antenna quality is a crucial factor in smartphone-based positioning
The use of an omnidirectional linearly polarized antenna in mobile devices has advantages in terms of received signal strength and the number of received signals (Pathak et al 2003), and makes the antenna very sensitive to multipath (MP) effects. This is generally accepted since the design drivers of smartphone antennas lead to seeking the highest sensitivity
The phase center offset (PCO) and phase center variations (PCV) corrections obtained from the calibration have been applied in the positioning algorithm of the GNSMART software to perform smartphone-based positioning
Summary
The Global Navigation Satellite System (GNSS) antenna quality is a crucial factor in smartphone-based positioning. The use of an omnidirectional linearly polarized antenna in mobile devices has advantages in terms of received signal strength and the number of received signals (Pathak et al 2003), and makes the antenna very sensitive to multipath (MP) effects. This is generally accepted since the design drivers of smartphone antennas (e.g., continuous signal reception in any location) lead to seeking the highest sensitivity.
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