Integrity Monitoring of PPP-RTK Positioning; Part I: GNSS-Based IM Procedure

Wang, Kan; El‐Mowafy, Ahmed; Qin, Weijin

doi:10.3390/rs14010044

Cited by 11 publications

(24 citation statements)

References 33 publications

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“…In this study, the risks of incorrect ambiguity fixing are considered as ignorable. While this assumption is widely used in existing studies (Jokinen et al, 2013a;Jokinen et al, 2013b;Feng et al, 2014;Wang et al, 2020;Wang et al 2022;Gao et al, 2021), the effects of wrong ambiguity fixing on the protection level computations are analyzed in Sect. "Effects of fault probabilities on protection level computations".…”

Section: Fault Modelsmentioning

confidence: 99%

“…Before the implementation, stochastic models, fault probabilities, PHMI, and false alarm rates should be defined priorly. Based on the existing research (Blanch et al, 2015;Racelis & Joerger, 2020;Wang et al, 2022;Working Group C, 2016), these parameters are set as in Table 3. It is worth mentioning that nominal biases and standard deviations of uncombined observations are still under investigation, we use a conservative setting which is usually used for IF combinations for them.…”

Section: Experimental Settingsmentioning

confidence: 99%

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Integrity monitoring scheme for single-epoch GNSS PPP-RTK positioning

Zhang

Wang

2023

Satell Navig

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Integrity monitoring for precise point positioning is critical for safety-related applications. With the increasing demands of high-accuracy autonomous navigation for unmanned ground and aerial vehicles, the integrity monitoring method of high-precision positioning has become an essential requirement. While high precision Global Navigation Satellite Systems (GNSS) positioning is widely used in such applications, there are still many difficulties in the integrity monitoring method for the multi-frequency multi-GNSS undifferenced and uncombined Precise Point Positioning (PPP). The main difficulties are caused by using the measurements of multiple epochs in PPP. Based on the baseline Multiple Hypothesis Solution Separation (MHSS) Advanced Receiver Autonomous Integrity Monitoring (ARAIM) algorithm, this paper discusses the feasibility of the pseudorange-based baseline ARAIM method on the single-epoch PPP based on Real-Time Kinematic (RTK) networks (PPP-RTK) framework to overcome these difficulties. In addition, a new scheme is proposed to transfer the conventional PPP process into the single-epoch PPP-RTK framework. The simulation results using the proposed model are analyzed in this study. The Protection Levels (PLs) estimated by PPP Wide-lane Ambiguity Resolution (PPP-WAR) model with regional corrections can reach the meter level and the PLs estimated by PPP Ambiguity Resolution (PPP-AR) and PPP-RTK models are usually the sub-meter level. Given a horizontal Alert Limit (AL) of 1.5 m, the global coverage of availability above 99.9% for PPP-WAR, PPP-AR, and PPP-RTK can reach 92.6%, 99.4%, and 99.7% respectively. The results using real kinematic data also show that tight PLs can be achieved when the observation conditions are good.

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Section: Fault Modelsmentioning

confidence: 99%

Section: Experimental Settingsmentioning

confidence: 99%

Integrity monitoring scheme for single-epoch GNSS PPP-RTK positioning

Zhang

Wang

2023

Satell Navig

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“…To ensure the precision of the ambiguity parameters, the ambiguity with a lower elevation angle of 15 degrees or with a STD value larger than one cycle will be rejected in the ambiguity resolution. In AR processing, the WL ambiguity is first fixed by rounding, and then the NL ambiguity by LAMBDA (Least-square AMBiguity Decorrelation Adjustment), with the ratio value threshold of 3 for ambiguity validation (Teunissen and Verhagen 2004;Wang et al 2022).…”

Section: Data and Experiments Descriptionmentioning

confidence: 99%

“…However, this STD may be vulnerable to gross error because it is calculated with few ionosphere observations. Wang et al (2022) analytically studied the form of the variancecovariance matrix of ionosphere interpolation errors for both accuracy and integrity purposes, which considers the processing noise, the ionosphere activities, and the network scale. How to properly determine the a priori precision for the interpolated ionospheric delay still needs further investigation.…”

Section: Introductionmentioning

confidence: 99%

PPP-RTK considering the ionosphere uncertainty with cross-validation

Cui

et al. 2022

Satell Navig

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With the high-precision products of satellite orbit and clock, uncalibrated phase delay, and the atmosphere delay corrections, Precise Point Positioning (PPP) based on a Real-Time Kinematic (RTK) network is possible to rapidly achieve centimeter-level positioning accuracy. In the ionosphere-weighted PPP–RTK model, not only the a priori value of ionosphere but also its precision affect the convergence and accuracy of positioning. This study proposes a method to determine the precision of the interpolated slant ionospheric delay by cross-validation. The new method takes the high temporal and spatial variation into consideration. A distance-dependent function is built to represent the stochastic model of the slant ionospheric delay derived from each reference station, and an error model is built for each reference station on a five-minute piecewise basis. The user can interpolate ionospheric delay correction and the corresponding precision with an error function related to the distance and time of each reference station. With the European Reference Frame (EUREF) Permanent GNSS (Global Navigation Satellite Systems) network (EPN), and SONEL (Système d'Observation du Niveau des Eaux Littorales) GNSS stations covering most of Europe, the effectiveness of our wide-area ionosphere constraint method for PPP-RTK is validated, compared with the method with a fixed ionosphere precision threshold. It is shown that although the Root Mean Square (RMS) of the interpolated ionosphere error is within 5 cm in most of the areas, it exceeds 10 cm for some areas with sparse reference stations during some periods of time. The convergence time of the 90th percentile is 4.0 and 20.5 min for horizontal and vertical directions using Global Positioning System (GPS) kinematic solution, respectively, with the proposed method. This convergence is faster than those with the fixed ionosphere precision values of 1, 8, and 30 cm. The improvement with respect to the latter three solutions ranges from 10 to 60%. After integrating the Galileo navigation satellite system (Galileo), the convergence time of the 90th percentile for combined kinematic solutions is 2.0 and 9.0 min, with an improvement of 50.0% and 56.1% for horizontal and vertical directions, respectively, compared with the GPS-only solution. The average convergence time of GPS PPP-RTK for horizontal and vertical directions are 2.0 and 5.0 min, and those of GPS + Galileo PPP-RTK are 1.4 and 3.0 min, respectively.

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“…Li et al [ 7 ] discovered that having more LEO satellites leads to a shorter convergence time, and the convergence time can be shortened from 8.2 to 0.8 min by introducing observations from 288 polar-orbiting LEO satellites. The results of Wang et al [ 8 , 9 ] showed that the LEO augmentation could be significantly reduced the convergence time of the ambiguity-float formal horizontal precision. Secondly, LEO signal augmentation can provide new observations.…”

Section: Introductionmentioning

confidence: 99%

A Novel Satellite PRN Code Assignment Method Based on Improved RLF Algorithm

Wang

Tian

Bian

et al. 2022

Sensors

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Low Earth Orbit (LEO) satellites have stronger received signals and more rapid geometry changes than Global Navigation Satellite System (GNSS) satellites, making them attractive for positioning, navigation, and timing (PNT) applications. Due to the low altitude, the LEO constellation requires more satellites to cover the entire globe and more Pseudo Random Noise (PRN) codes to realize Code Division Multiple Access (CDMA), which means greater receiver storage resources and receiver acquisition time. In this paper, different from the traditional methods that assign a unique PRN code to each satellite, we propose a novel method in which several satellites share the same PRN code, and simply demonstrate the feasibility and benefits of this method. To determine the minimum number of PRN codes needed for a constellation, we build a mathematical model. After the algorithm comparison, we improve the recursive largest first (RLF) algorithm so that it has a higher running speed and a smaller approximate optimal solution within a certain time period. By studying polar-orbiting and walker constellations, we find that if other satellite parameters remain the same, the higher the orbital altitude is, the more PRN codes are needed, and no matter what the orbital inclination is, the minimum number of PRN codes remains the same. Overall, it is feasible and meaningful for several satellites sharing the same PRN code to save storage resources and reduce the satellite acquisition time of the receiver. If this new technology is applied, the storage resources and the average satellite acquisition time of the receiver will be, at most, one-third of previous ones.

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Integrity Monitoring of PPP-RTK Positioning; Part I: GNSS-Based IM Procedure

Cited by 11 publications

References 33 publications

Integrity monitoring scheme for single-epoch GNSS PPP-RTK positioning

Integrity monitoring scheme for single-epoch GNSS PPP-RTK positioning

PPP-RTK considering the ionosphere uncertainty with cross-validation

A Novel Satellite PRN Code Assignment Method Based on Improved RLF Algorithm

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