A New Algorithm for High-Integrity Detection and Compensation of Dual-Frequency Cycle Slip under Severe Ionospheric Storm Conditions

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.

Improved Cycle Slip Repair with GPS Triple-Frequency Measurements by Minifying the Influences of Ionospheric Variation and Pseudorange Errors

“…Furthermore, the second-order difference of ionospheric delay can be designed to investigate the characteristics of the ionospheric variation [10,20,24], and is expressed as:…”

“…In particular, when the large pseudorange error gives rise to a significant bias on the HMW of more than the tolerable limitation, the result of CSD with HMW may lead to a misjudgment. On the other hand, as the GF contains the influence of ionospheric delay, the severe ionospheric variation threatens the correctness of CSD with GF [10,11]. Since the ionospheric variation produces a remarkable bias on the GF larger than the tolerable limitation, serious degradation occurs in the reliability of CSD with GF.…”

“…In situations of processing a single satellite data, some repair methods with hybrids of HMW and GF achieved better CSR performance [10,19,20]. Through filtering and smoothing, the ionospheric variation could be corrected in the GF.…”

Improving the Accuracy of Regional Ionospheric Mapping with Double-Difference Carrier Phase Measurement

“…During the preprocessing stage, cycle slip detection is carried out to prevent an unexpected jump in the carrier phase measurement. The cycle slip can be detected by monitoring the acceleration of the ionospheric delay because it is less than 10 −4 m/s 2 [16][17][18]. Unexpected outliers are detected by using the second derivative of the geometry-free combination of the carrier phase as a monitoring value.…”

Covariance Analysis of Real-Time Precise GPS Orbit Estimated from Double-Differenced Carrier Phase Observations

“…In recent years, precise real-time global positioning system (GPS) orbit products have extended the capability to support real-time applications such as autonomous driving, intelligent transportation systems, and collision avoidance [1,2]. The real-time precision of orbits enables navigation systems to overcome problems arising from orbit errors in real-time observations [3].…”