Abstract
Many strategies for treating dual-frequency cycle slip, which can seriously affect the performance of a carrier-phase-based positioning system, have been studied over the years. However, the legacy method using the Melbourne-Wübbena (MW) combination and ionosphere combination is vulnerable to pseudorange multipath effects and high ionospheric storms. In this paper, we propose a robust algorithm to detect and repair dual-frequency cycle slip for the network-based real-time kinematic (RTK) system which generates high-precision corrections for users. Two independent and complementary carrier-phase combinations, called the ionospheric negative and positive combinations in this paper, are employed for avoiding insensitive pairs. In addition, they are treated as second-order time differences to reduce the impact of ionospheric delay even under severe ionospheric storm. We verified that the actual error distributions of these monitoring values can be sufficiently bounded by the normal Gaussian distribution. Consequently, we demonstrated that the proposed method ensures high-integrity performance with a maximum probability of missed detection of 7.5 × 10−9 under a desired false-alarm probability of 10−5. Furthermore, we introduce a LAMBDA-based cycle slip compensation method, which has a failure rate of 1.4 × 10−8. Through an algorithm verification test using data collected under a severe ionospheric storm, we confirmed that artificially inserted cycle slips are successfully detected and compensated for. Thus, the proposed method is confirmed to be effective for handling dual-frequency cycle slips of the network RTK system.
Highlights
The demand for high-precision navigation systems employing carrier-phase observations has been growing rapidly for applications such as automated vehicle driving and monitoring, collision avoidance, and intelligent transportation systems [1]
As a first step to enhancing the network-based real-time kinematic (RTK) system, we focus on the high-integrity detection algorithm for continuously operating reference stations (CORS)
In order to evaluate the performance of the proposed identification method, we calculate the probability of failure, which refers to the probability that the float solution is pulled to a wrong integer cycle slip
Summary
The demand for high-precision navigation systems employing carrier-phase observations has been growing rapidly for applications such as automated vehicle driving and monitoring, collision avoidance, and intelligent transportation systems [1]. Most dual-frequency insensitive cycle-slip pairs can be detected by the MW combination and ionosphere combination This detection algorithm can be used for static and even dynamic users because of the benefit of geometry-free combination; it has critical limitations when detecting small cycle slips. The probability of occurrence of these insensitive pairs is incredibly small [10], but it is still considered an integrity threat to a system requiring high-integrity performance To overcome these limitations, triple-frequency signals, which allow many additional combinations such as the extra-wide lane combination and ionospheric reduced combination, are being emphasized for improving performance [17,18,19,20,21]. Song and Kee demonstrated that there is no additional geometry-free carrier-phase combination to replace the MW combination for dynamic users [14]; geometry-based combinations can be employed in static permanent stations for generating reliable high-precision corrections.
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