Explore the vast range of titles available.

Autonomous driving is becoming a pivotal technology that can realize intelligent transportation and revolutionize the future of mobility. Various types of sensors, including perception sensors and localization sensors, are essential for high-level autonomous and intelligent vehicles (AIV). In this paper, the characteristics of different sensors are compared, and the application characteristics and requirements of AIV are analyzed in depth. These analyses indicate that: GNSS, as the unique localization sensor that can obtain an absolute position, can not only provide all-weather position and time information for internal multi-sensor fusion but also act as a standard spatiotemporal reference for all autonomous systems; Furthermore, AIVs aim to provide safety for a mass user base ranging from tens to hundreds of millions; for this, AIVs require a global wide-area and instantaneous precise positioning service with location privacy protection. Based on a “geometry-bound” description of road grade and vehicle size, it has been found that GNSS requirements in autonomous vehicles include decimeter-level positioning with the assurance of high integrity. Combined with high-integrity GNSS implementation in the civil aviation field, GNSS different technology routes, and commercial solutions, a state space representation (SSR)-based GNSS high-precision augmentation positioning solution for AIV is summarized and introduced. The solution can achieve instantaneous, precise positioning with high integrity in a wide area by utilizing passive positioning mode with location privacy protection. In addition, the research progress on key technologies in the solution and existing challenges is investigated in detail by reviewing a series of publications.

LEO augmentation systems are attracting worldwide attention. However, their performance in real-world environments has not yet been reported, although several systems have already launched experimental satellites, such as the CENTISPACE™ system developed by Beijing Future Navigation Tech Co., Ltd. By using real observations from two experimental CENTISPACE™ satellites recorded by a regional network, we present the results of LEO-enhanced precise point positioning (PPP) performance. Based on a proposed three-step approach for LEO orbit determination and time synchronization, a framework for LEO augmentation data processing is established and validated. Two stations are selected for LEO augmentation evaluation, and static PPP is performed by combining the LEO augmentation observations with different GNSS systems, including GPS, BDS-3, and Galileo. The static PPP precision shows a few improvements attributed to LEO observations; the positioning errors with one, two, and three GNSS systems are 6.1, 4.6, and 4.6 cm, respectively, while they are reduced to 5.2, 3.9, and 3.8 cm by adding the LEO satellites, respectively, revealing improvements of 13.9, 16.4, and 18.8%, respectively. Moreover, PPP convergence is significantly enhanced. The average convergence times with one, two, and three GNSS systems are 32.7, 17.9, and 14.2 min, respectively, which are reduced to 16.7, 8.9, and 5.7 min, respectively, by adding LEO observations. This indicates that the convergence time is significantly shortened by approximately 53% with the augmentations from only two LEO satellites. Such results show the potential of LEO augmentation, and larger improvements can be expected with more LEO satellites to be deployed in the future.

Within the framework of differential augmentation, this paper introduces the basic technical framework and performance of the BeiDou Global Navigation Satellite System (BDS-3) Satellite-Based Augmentation System (BDSBAS), including orbit products, satellite clock offset products, ionosphere and its integrity performance. The basic principle of BDS-3 Precise Point Positioning (PPP-B2b) is expounded, the similarities and differences between the PPP service provided by BDS-3 and International Global Navigation Satellite System (GNSS) Service (IGS) are discussed, and the limitations of PPP-B2b are analyzed. Since both the BDSBAS and PPP-B2b utilize a ground monitoring station network to determine the satellite orbits and clock offset corrections, and broadcast differential corrections through the three Geostationary Orbit (GEO) satellites of BDS-3, the feasibility of the co-construction of BDSBAS and PPP-B2b is analyzed, strategies for the infrastructure sharing and correction broadcasting are presented, and the influences of BDSBAS correction broadcasting strategy adjustment are evaluated. In addition, it assesses the possibility of broadcasting differential corrections through the Inclined Geosynchronous Orbit (IGSO) satellites of BDS-3, and the feasibility of augmenting satellite navigation with Low Earth Orbit (LEO) satellites.

To enable the use of global navigation satellite systems (GNSSs) for aircraft navigation, satellite-based augmentation systems have been implemented worldwide to guarantee the accuracy and integrity of aircraft position estimates derived from observations of GNSS signals. For over two decades, the United States’ Wide Area Augmentation System (WAAS) has protected users of the Global Positioning System from threats to position accuracy posed by ionospheric disturbances over North America. A prior companion paper (Sparks et al., 2022) reviews how WAAS has protected users from the disruptive impact of moderate and extreme iono spheric storms. The present paper addresses the methodology adopted by WAAS to protect users from the influence of ionospheric disturbances that are more modest in magnitude, both those well-sampled and those poorly sampled. A subsequent companion paper traces in greater detail the evolution of the WAAS undersampled ionospheric irregularity threat model used to augment the integrity confidence bounds that quantify position accuracy.

Precise point positioning (PPP) can be significantly improved with the multi- multi-GNSS constellation, but it still takes more than 10 min to obtain positioning results at centimeter-level accuracy. We develop a multi-constellation (GPS + GLONASS + Galileo + BDS) PPP ambiguity resolution (AR) method augmented by precise atmospheric corrections to achieve instantaneous centimeter-level positioning. In the proposed method, multi-constellation PPP fixed solutions are carried out at the reference network. The precise tropospheric delays are derived from the ionospheric-free (IF) phase observations while the slant ionospheric delays are extracted from the raw phase observations after the ambiguities are fixed. Afterward, they are provided to user stations for correcting the raw observations. Using these precise atmospheric corrections, one can achieve an instantaneous ambiguity resolution (IAR) with an accuracy of several centimeters. This method is validated experimentally with the Australian Regional GPS Network (ARGN), the South Pacific Regional GNSS Network (SPRGN) and the Hong Kong CORS. The ambiguity resolution can be achieved in several seconds with regionally computed atmospheric corrections, and the convergence time of positioning is significantly shortened compared to the PPP float and PPP-AR solution. Besides, the regional augmentation PPP (RA-PPP) also provides an advantage over network real-time kinematic (NRTK); the time to first ambiguity resolution can be shortened from 3 epochs to 1 epoch. The results also demonstrate the contribution of multi-constellation fusion to the PPP IAR in terms of positioning accuracy and reliability. The percentage of IAR can be up to 90.0% for multi-GNSS solutions, while the percentage for GPS-only solution is 7.2% when the cutoff elevation angle is 40°.

Precise point positioning (PPP) is receiving increasing interest due to its cost-effectiveness, global coverage and high accuracy. However, its application in the urban environment is still full of challenges due to the satellite tracking sky-view. Thus, we presented a comprehensive positioning model by fusing the multi-GNSS (global navigation satellite system) combination, GNSS/INS (inertial navigation system) tightly coupled integration as well as the ionospheric and tropospheric augmentation in the undifferenced and uncombined PPP. The performance of this model in dual-frequency and single-frequency positioning was assessed with two experiments that denoted as T019 and T023, respectively, and both the experiments were carried out in a real urban environment. Particularly, the experiment T023 was carried out in the Second Ring Road of Wuhan city, which can be regarded as a typical downtown environment. Concerning the regional atmospheric augmentation, observations from 5 reference stations with an inter-station distance of about 40 km were also collected during the experimental time. The comparison between reference stations suggested that the regional tropospheric model had a precision of better than 0.6 cm in terms of zenith tropospheric delay, while the regional ionospheric model had a precision of around 0.5 total electron content unit in terms of Vertical Total Electron Content. It can be concluded that the GPS-only PPP can be improved significantly for urban vehicle navigation with these techniques, i.e., the multi-GNSS, INS tightly coupled integration and the atmospheric augmentation, through the positioning analysis, while INS tightly coupled integration makes the most contributions under the downtown environment, and the improvement of the regional atmospheric augmentation in single-frequency PPP is more significant since that single frequency is more sensitive to the ionospheric delay. In addition, it is proved that the regional atmospheric augmentation accelerates positioning convergence. The 3D positioning root-mean-square (RMS) with the comprehensive positioning model for dual frequency are 0.22 m and 0.77 m for T019 and T023, respectively. Concerning single-frequency PPP, the 3D RMS is 0.45 m and 1.17 m for T019 and T023, respectively. Moreover, taking the lane-level navigation under the downtown environment of T023 into consideration, we further presented the cumulative frequency of the horizontal positioning error less than 1 m, i.e., P d N 2 + d E 2 < 1 m , and the best solution can be found with PPP by fusing all the techniques, in which P d N 2 + d E 2 < 1 m is 99.0% and 93.2% for dual frequency and single frequency, respectively.

Satellite-based augmentation systems ensure the accuracy and integrity of aircraft position estimates derived from radio signals broadcast by the Global Navigation Satellite System. The United States’ Wide Area Augmentation System (WAAS) protects users of the Global Positioning System from threats generated by ionospheric disturbances. The means by which WAAS mitigates these threats depends upon their magnitude. This paper addresses: a) how WAAS monitors the level of ionospheric perturbation over North America; b) how various availability and integrity concerns have influenced the implementation of WAAS’s extreme and moderate ionospheric storm detectors; c) how the algorithms governing these implementations have evolved since WAAS’s commissioning in 2003; and d) how the largest ionospheric storms of the past two solar cycles can be ranked according to their impact on WAAS. A subsequent companion paper will address the evolution of the WAAS methodology for protecting users from the adverse influence of more moderate ionospheric disturbances.

Abstract The Wide Area Augmentation System (WAAS) renders the United States’ Global Positioning System (GPS) safe and reliable for aircraft navigation over North America. This paper is the third in a sequence of companion papers providing a comprehensive review of how WAAS, over the first 20 years of its operation, has mitigated threats posed by the ionosphere to the accuracy and integrity of position estimates derived from measurements of GPS signals. The initial paper (Sparks et al., 2022) reviews how WAAS has protected the user from threats generated by large-scale ionospheric storms. The second paper (Sparks et al., 2026) provides an overview of the methodology WAAS has applied to protect the user from the potentially harmful impact of ionospheric disturbances that are more modest in magnitude. This paper traces the evolution of the undersampled ionospheric irregularity threat model used by WAAS to augment the integrity confidence bounds that confine the user’s positioning error.

Global Navigation Satellite Systems provide autonomous vehicles with precise position information through the process of position augmentation. This paper presents a series of performance tests aimed to compare the position accuracy of augmentation techniques such as classical Differential Global Navigation Satellite System, Real-time Kinematic and Real-time eXtended. The aim is to understand the limitations and choose the best position augmentation technique in order to obtain accurate, trustworthy position estimates of a vehicle in urban environments. The tests are performed in and around the German cities of Wuppertal and Duesseldorf, using a vehicle fitted with the navigation system POS-LV 220, developed by Applanix Corporation. In order to evaluate the real-time performance of position augmentation techniques in a highly challenging environment, a total of four test regions are selected. The four test regions are characterized mainly by uneven terrain with tall buildings around the University of Wuppertal, flat terrain with roads of varying width in the city centre of Wuppertal and Duesseldorf and flat terrain in a tunnel section located in the city of Wuppertal. The performances of the different position augmentation are compared using a Root Mean Square (RMS) error estimate obtained as an output from the Applanix system. Furthermore, a High-Definition map of the environment is used for the purpose of model validation, which justifies the use of RMS error estimate as an evaluation metric for the performance analysis tests. According to the performance tests carried out as per the conditions specified in this paper, the Real-time eXtended (RTX) position augmentation method enables to obtain a more robust position information of the vehicle than Real-time Kinematic (RTK) method, with a typical accuracy of a few centimeter in an urban environment.

Space-based augmentation system (SBAS) provides correction information for improving the global navigation satellite system (GNSS) positioning accuracy in real-time, which includes satellite orbit/clock and ionospheric delay corrections. At SBAS service area boundaries, the correction is not fully available to GNSS users and only a partial correction is available, mostly satellite orbit/clock information. By using the geospatial correlation property of the ionosphere delay information, the ionosphere correction coverage can be extended by a spatial extrapolation algorithm. This paper proposes extending SBAS ionosphere correction coverage by using a biharmonic spline extrapolation algorithm. The wide area augmentation system (WAAS) ionosphere map is extended and its ionospheric delay error is compared with the GPS Klobuchar model. The mean ionosphere error reduction at low latitude is 52.3%. The positioning accuracy of the extended ionosphere correction method is compared with the accuracy of the conventional SBAS positioning method when only a partial set of SBAS corrections are available. The mean positioning error reduction is 44.8%, and the positioning accuracy improvement is significant at low latitude.