Abstract
Multipath detection and mitigation are crucial issues for global navigation satellite system (GNSS) high-precision positioning. The multi-frequency carrier power-to-noise density ratio (C/N0)-based multipath detection technique has achieved good results in real-time static and low-dynamic applications, and shown better practicability because of the low computational load and the requirement for little additional hardware. However, the classic multipath detection method based on inter-frequency C/N0 differences directly employs the 3σ rule to determine the threshold without considering the distribution of detection statistics and their variation characteristics with elevation angle, and ignores the interference of outliers to the reference functions. A robust multipath detection method is proposed in this paper. The reference functions of C/N0 differences are fitted using least absolute deviation (LAD) to obtain more accurate nominal values. According to the skew characteristics of the detection statistics, a medcouple (MC)-based adjusted boxplot is employed to determine the threshold. The performance of the new detection method is verified in the multipath environments. The experimental results show that compared with the classic method, the new multipath detector has strong robustness and can respond more accurately to large changes in multipath (MP) combination values at most elevation angles. It is sensitive to short-delay multipath and diffraction, and is an important supplement to multipath detection techniques.
Highlights
Multipath is one of the most problematic factors that restricts the accuracy and reliability of global navigation satellite system (GNSS) positioning, especially in challenging environments, such as urban canyons, viaducts, high-rise glass buildings and wooded areas
A robust multipath detection method is proposed in this paper and compared to the classic 3σ method using inter-frequency C/N0 differences
It is difficult for ordinary least squares (OLS) to resist the influence of outliers on the calibration data, which makes the reference function deviate to the outliers
Summary
Multipath is one of the most problematic factors that restricts the accuracy and reliability of global navigation satellite system (GNSS) positioning, especially in challenging environments, such as urban canyons, viaducts, high-rise glass buildings and wooded areas. Short-delay multipath is defined as reflected signal delays less than 0.1 chips (about 30 m for the GPS L1 C/A case) and long-delay multipath covers the reflected signal delays greater than 0.75 chips [1]. The latter can be distinguished by the code tracking loop of a GPS receiver, while short-delay multipath is often difficult to handle due to the strong correlation between its signal and the LOS signal [2]. Multi-frequency carrier power-to-noise density ratio (C/N0)-based multipath detection shows great potential in real-time applications because it does not require additional hardware and the computational load is low [13,14]
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