Cycle Slip Detection and Repair for Dual-Frequency LEO Satellite GPS Carrier Phase Observations with Orbit Dynamic Model Information

Cycle slip detection and repair are crucial for precise GPS-derived orbit determination of the low-Earth orbit (LEO) satellites. We present a new approach to detect and repair cycle slips for dual-frequency LEO satellite GPS observations. According to Newton’s equation of motion, the second-order time difference of the LEO satellite’s position (STP) is only related to the sampling interval and the satellite’s acceleration, which can be precisely obtained from the known orbit dynamic models. Then, several kinds of second-order time-difference geometry-free (STG) phase combinations, taking full advantage of the correlation between the satellite orbit variations and the dynamic model, with different level of ionospheric residuals, are proposed and adopted together to detect and fix cycle slips. The STG approach is tested with some LEO satellite GPS datasets. Results show that it is an effective cycle slip detection and repair method for LEO satellite GPS observations. This method also has some important features. Firstly, the STG combination is almost independent of the pseudorange. Secondly, this method is effective for LEO satellites, even in real-time application. Thirdly, this method is suitable for ground-based GPS receivers if we know the acceleration of the receivers.

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A New Cycle Slip Detection and Repair Method Using a Single Receiver’s Single Station B1 and L1 Frequencies in Ground-Based Positioning Systems

Sensors ◽

10.3390/s20020346 ◽

2020 ◽

Vol 20 (2) ◽

pp. 346

Author(s):

Xinyang Zhao ◽

Zun Niu ◽

Gaoxu Li ◽

Qiangqiang Shuai ◽

Bocheng Zhu

Keyword(s):

Carrier Phase ◽

Outdoor Environment ◽

Cycle Slip ◽

Dual Frequency ◽

Positioning Systems ◽

Cycle Slips ◽

Single Station ◽

Cycle Slip Detection ◽

Phase Combination ◽

Slip Detection

The detection and repair of the cycle slip is a key step for high precision navigation and positioning in indoor environments. Different methods have been developed to detect and repair cycle slips for carrier phase processing. However, most approaches are designed to eliminate the effects of the ionosphere in an outdoor environment, and many of them use pseudorange (code) information that is no longer suitable for indoor multipath environments. In this paper, a method based on the geometry-free combination without the pseudorange data is proposed to detect and fix cycle slips. A ground-based navigation system is built for data collection. Unlike the traditional dual-frequency cycle slip detection method, the Beidou B1, GPS L1 carrier phase combination is used instead of the B1, B2, or L1, L2 carrier phase combination, Ublox is used for data collecting. For fixing the cycle slips quickly, an improved adaptive Particle Swarm Optimization (PSO) algorithm is employed. We compared the performance of the new method with the existing two methods using simulated data in different conditions. The results show that the proposed method has better performance than other methods.

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A Modified TurboEdit Cycle-Slip Detection and Correction Method for Dual-Frequency Smartphone GNSS Observation

Sensors ◽

10.3390/s20205756 ◽

2020 ◽

Vol 20 (20) ◽

pp. 5756

Author(s):

Xiaofei Xu ◽

Zhixi Nie ◽

Zhenjie Wang ◽

Yuanfan Zhang

Keyword(s):

Correction Method ◽

Least Square ◽

Cycle Slip ◽

Dual Frequency ◽

Cycle Slips ◽

Small Cycle ◽

Cycle Slip Detection ◽

Gnss Receivers ◽

Wide Lane ◽

Slip Detection

Recently, some smartphone manufacturers have subsequently released dual-frequency GNSS smartphones. With dual-frequency observations, the positioning performance is expected to be significantly improved. Cycle-slip detection and correction play an important role in high-precision GNSS positioning, such as precise point positioning (PPP) and real-time kinematic (RTK) positioning. The TurboEdit method utilizes Melbourne–Wübbena (MW) and phase ionospheric residual (PIR) combinations to detect cycle-slips, and it is widely used in the data processing applications for geodetic GNSS receivers. The smartphone pseudorange observations are proved to be much noisier than those collected with geodetic GNSS receivers. Due to the poor pseudorange observation, the MW combination would be difficult to detect small cycle-slips. In addition, some specific cycle-slip combinations, where the ratio of cycle-slip values at different carrier frequencies is close to the frequency ratio, are also difficult to be detected by PIR combination. As a consequence, the traditional TurboEdit method may fail to detect specific small cycle-slip combinations. In this contribution, we develop a modified TurboEdit cycle-slip detection and correction method for dual-frequency smartphone GNSS observations. At first, MW and PIR combinations are adopted to detect cycle-slips by comparing these two combinations with moving-window average values. Then, the epoch-differenced wide-lane combinations are used to estimate the changes of smartphone position and clock bias, and the cycle-slip is identified by checking the largest normalized residual whether it exceeds a predefined threshold value. The process of estimation and cycle-slip identification is implemented in an iterative way until there is no over-limit residual or there is no redundant measurement. At last, the cycle-slip values at each frequency are estimated with the epoch-differenced wide-lane and ionosphere-free combinations, and the least-square ambiguity decorrelation adjustment (LAMBDA) method is adopted to further obtain an integer solution. The proposed method has been verified with 1 Hz dual-frequency smartphone GNSS data. The results show that the modified TurboEdit method can effectively detect and correct even for specific small cycle-slip combinations, e.g., (4, 3), which is difficult to be detected with the traditional TurboEdit method.

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Algorithm for Real-Time Cycle Slip Detection and Repair for Low Elevation GPS Undifferenced Data in Different Environments

Remote Sensing ◽

10.3390/rs13112078 ◽

2021 ◽

Vol 13 (11) ◽

pp. 2078

Author(s):

Ning Liu ◽

Qin Zhang ◽

Shuangcheng Zhang ◽

Xiaoli Wu

Keyword(s):

Real Time ◽

High Voltage ◽

Second Order ◽

Cycle Slip ◽

Order Difference ◽

Cycle Slips ◽

Cycle Slip Detection ◽

Wide Lane ◽

Time Cycle ◽

Slip Detection

Real-time cycle slip detection and repair is one of the key issues in global positioning system (GPS) high precision data processing and application. In particular, when GPS stations are in special environments, such as strong ionospheric disturbance, sea, and high-voltage transmission line interference, cycle slip detection and repair in low elevation GPS observation data are more complicated than those in normal environments. For low elevation GPS undifferenced carrier phase data in different environments, a combined cycle slip detection algorithm is proposed. This method uses the first-order Gauss–Markov stochastic process to model the pseudorange multipath in the wide-lane phase minus narrow-lane pseudorange observation equation, and establishes the state equation of the wide-lane ambiguity with the pseudorange multipath as a parameter, and it uses the Kalman filter for real-time estimation and detects cycle slips based on statistical hypothesis testing with a predicted residual sequence. Meanwhile, considering there are certain correlations among low elevation, observation epoch interval, and ionospheric delay error, a second-order difference geometry-free combination cycle slip test is constructed that takes into account the elevation. By combining the two methods, real-time cycle slip detection for GPS low elevation satellite undifferenced data is achieved. A cycle slip repair method based on spatial search and objective function minimization criterion is further proposed to determine the correct solution of the cycle slips after they are detected. The whole algorithm is experimentally verified using the static and kinematic measured data of low elevation satellites under four different environments: normal condition, high-voltage transmission lines, dynamic condition in the sea, and ionospheric disturbances. The experimental results show that the algorithm can detect and repair cycle slips accurately for low elevation GPS undifferenced data, the difference between the float solution and the true value for the cycle slip does not exceed 0.5 cycle, and the differences obey the normal distribution overall. At the same time, the wide-lane ambiguity and second-order difference GF combination sequence calculated by the algorithm is smoother, which give further evidence that the algorithm for cycle slip detection and repair is feasible and effective, and has the advantage of being immune to the special observation environments.

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Cycle Slip Detection and Ambiguity Resolution Algorithms for Dual-Frequency GPS Data Processing

Marine Geodesy ◽

10.1080/014904199273443 ◽

1999 ◽

Vol 22 (3) ◽

pp. 169-181 ◽

Cited By ~ 33

Author(s):

Yang Gao, Zuofa Li

Keyword(s):

Data Processing ◽

Ambiguity Resolution ◽

Gps Data ◽

Cycle Slip ◽

Dual Frequency ◽

Cycle Slip Detection ◽

Gps Data Processing ◽

Slip Detection

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Data pre-processing for ionosphere TEC retrieval based on DORIS observations

10.5194/egusphere-egu2020-21943 ◽

2020 ◽

Author(s):

Shaocheng Zhang ◽

Wei Li ◽

Fei Yin ◽

Hongfei Gou

Keyword(s):

Precise Orbit Determination ◽

Low Earth Orbit ◽

Cycle Slip ◽

Dual Frequency ◽

Phase Measurements ◽

Cycle Slip Detection ◽

Low Earth Orbit Satellites ◽

Signal Path ◽

Leo Satellite

&#160;DORIS system aims to provide precise orbit determination of low earth orbit satellites, and the dual-frequencies on S1=2036.25 MHz and U2=401.25 MHz were used on DORIS signals. The ionosphere TEC retrieval on the signal path is possible based on DORIS dual-frequency observations.Analysis results show that DORIS pseudo-ranges had noise with several kilometers level, hence only the carrier-phase observations could be utilized on TEC retrieval. Moreover, as the DORIS ground stations were thousands kilometers separated with each other, station differential cannot be guaranteed and the data preprocessing can only be done base on the un-difference observations before the TEC could be precisely determined.In this research, a polynomial function was applied to model the DORIS phase observations, and minimal detectable biases (MDB) of less than one cycle wavelength was used as the index on the cycle-slip detection. And then the geometry free combination of S1 and U2 phase measurements were calculated for each DORIS LEO satellite passing arc. Finally, the unknown ambiguities bias on S1 and U2 geometry free observables were shifted to coincide with STEC calculated from the IGS GIM products.Both the Jason-2 & 3 based DORIS observations were used for the validation, several simulated +5 and -1 cycle-slip events on both DORIS observation could be clearly detected and correctly repaired. And the calculated STEC on one satellite passing arc from the LEO satellite to station show well agreement with IGS STEC on continent area, and the differences on ocean areas could be used to prove that the IGS GIM products were less precise on those areas.

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Instantaneous Triple-Frequency GPS Cycle-Slip Detection and Repair

International Journal of Navigation and Observation ◽

10.1155/2009/407231 ◽

2009 ◽

Vol 2009 ◽

pp. 1-15 ◽

Cited By ~ 36

Author(s):

Zhen Dai ◽

Stefan Knedlik ◽

Otmar Loffeld

Keyword(s):

Time Algorithm ◽

Cycle Slip ◽

High Data ◽

Cycle Slips ◽

Triple Frequency ◽

Test Criteria ◽

Cycle Slip Detection ◽

Phase Data ◽

Low Phase Noise ◽

Slip Detection

A real-time algorithm to detect, determine, and validate the cycle-slips for triple-frequency GPS is proposed. The cycle-slip detection is implemented by simultaneously applying two geometry-free phase combinations in order to detect more insensitive cycle-slips, and it is applicable for high data rate applications. The cycle-slip determination adaptively uses the predicted phase data and the code data. LAMBDA technique is applied to search for the cycle-slip candidates. The cycle-slip validation provides strict test criteria to identify the cycle-slip candidates under low phase noise. The reliability of the proposed algorithms is tested in different simulated scenarios.

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A New Cycle Slip Detection and Repair Method for Single-Frequency GNSS Data

Journal of Navigation ◽

10.1017/s0373463318000243 ◽

2018 ◽

Vol 71 (6) ◽

pp. 1492-1510 ◽

Cited By ~ 3

Author(s):

Qusen Chen ◽

Hua Chen ◽

Weiping Jiang ◽

Xiaohui Zhou ◽

Peng Yuan

Keyword(s):

Satellite System ◽

Single Frequency ◽

Half Cycle ◽

Cycle Slip ◽

Cycle Slips ◽

Small Cycle ◽

Cycle Slip Detection ◽

Gnss Data ◽

The Impact ◽

Slip Detection

Cycle slip detection for single frequency Global Navigation Satellite System (GNSS) data is currently mainly based on measurement modelling or prediction, which cannot be effectively performed for kinematic applications and it is difficult to detect or repair small cycle slips such as half-cycle slips. In this paper, a new method that is based on the total differential of ambiguity and Least-Squares Adjustment (LSA) for cycle slip detection and repair is introduced and validated. This method utilises only carrier-phase observations to build an ambiguity function. LSA is then conducted for detecting and repairing cycle slips, where the coordinate and cycle slips are obtained successively. The performance of this method is assessed through processing short and long baselines in static and kinematic modes and the impact of linearization and atmospheric errors are analysed at the same time under a controlled variable method. The results indicate this method is very effective and reliable in detecting and repairing multiple cycle slips, especially small cycle slips.

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An Enhanced Method for Detecting and Repairing the Cycle Slips of Dual-Frequency Onboard GPS Receivers of LEO Satellites

Journal of Sensors ◽

10.1155/2020/8817626 ◽

2020 ◽

Vol 2020 ◽

pp. 1-17

Author(s):

Zhouming Yang ◽

Xin Liu ◽

Jinyun Guo ◽

Yaowei Xia ◽

Xiaotao Chang

Keyword(s):

Weighted Least Squares ◽

Observation Equation ◽

Single Frequency ◽

Observation Data ◽

Cycle Slip ◽

Dual Frequency ◽

Gps Receivers ◽

Cycle Slips ◽

Reference Satellite ◽

Leo Satellites

Cycle slip detection and repair play important roles in the processing of data from dual-frequency GPS receivers onboard low-Earth orbit (LEO) satellites. To detect and repair cycle slips more comprehensively, an enhanced error method (EEM) is proposed. EEM combines single-frequency and narrow-lane carrier phase observations to construct special observations and observation equation groups. These special observations differ across time and satellite (ATS). ATS observations are constructed by three steps. The first step is differencing single-frequency and narrow-lane observations through a time difference (TD). The second step is to select a satellite as a reference satellite and other satellites as nonreference satellites. The third step is to difference the single-frequency TD observations from the reference satellite and the narrow-lane TD observations from the nonreference satellites by a satellite difference. If cycle slips occur at the reference satellite, the correction values for these ATS observations can be significantly enlarged. To process all satellites, the EEM selects each satellite as a reference satellite and builds the corresponding equation group. The EEM solves these observation equation groups according to the weighted least-squares adjustment (LSA) criterion and obtains the correction values; these correction values are then used to construct the χ 2 values corresponding to different equation groups, and the EEM subsequently carries out a chi-square distribution test for these χ 2 . The satellite corresponding to the maximum χ 2 will be marked. Then, the EEM iteratively processes the other satellites. Cycle slips can be estimated by rounding the float solutions of changes in the ambiguities of cycle slip satellites to the nearest integer. The simulation test results show that the EEM can be used to detect special cycle slip pairs such as (1, 1) and (9, 7). The EEM needs only observation data in two adjacent epochs and is still applicable to observation epochs with continuous cycle slips.

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