GNSS augmentation

About: GNSS augmentation is a research topic. Over the lifetime, 2478 publications have been published within this topic receiving 28513 citations. The topic is also known as: SBAS & Satellite Based Augmentation System.

Accelerated collective detection technique for weak GNSS signal environment

Abstract: Collective Detection is an Assisted-GNSS (A-GNSS) technique for direct positioning, where the information from all satellites in view is combined to enable rapid acquisition and a direct navigation solution. This technique is shown to perform effectively in weak signal environments like indoor navigation, reducing the required signal strength by 10 to 20 dB-Hz. When the signal from satellites cannot be acquired individually, Collective Detection constructively adds information from each satellite together, thus improving sensitivity and directly leading to a position solution. In a sense, the vector-based approach used generally in tracking, is extended to the acquisition stage. However, the existing Collective Detection techniques are computationally intensive and thus have limited practical applications. Also, the transmit-time assistance provided to the receiver is assumed to be of sub-millisecond accuracy, which is not a feasible assumption. This paper looks at these limitations of Collective Detection and aims to mitigate them under the assumption that at least one satellite can be acquired individually. It has been shown that the proposed Accelerated Collective Detection is faster and more efficient than the traditional scheme, and performs equally well in terms of accuracy.

GNSS/INS/Star Tracker Integrated Navigation System for Earth-Moon Transfer Orbit

Abstract: Over the last few years, new Global Navigation Satellite System (GNSS) applications have emerged that go far beyond the original objectives of GNSS which was providing position, velocity and timing (PVT) services for land, maritime, and air applications. Indeed, today, GNSS is used in Low Earth Orbit (LEO) for a wide range of applications such as real-time navigation, formation flying, precise time synchronization, orbit determination and atmospheric profiling. GNSS, in fact, can maximize the autonomy of a spacecraft and reduce the burden and costs of network operations. For this reason, there is a strong interest to also use GNSS for High Earth Orbit or Highly Elliptical Orbit (HEO) missions. However, the use of GNSS for HEO up to Moon altitudes is still new, and terrestrial GNSS receivers have not been designed to cope with the space environment which affects considerably the GNSS receiver performance and the GNSS solution (e.g. navigation solution). The goal of our research is therefore to develop a proof of concept of a spaceborne GNSS receiver for Earth-Moon transfer orbits, assisted by Inertial Navigation System (INS), a Star Tracker and an orbital forces model to increase the navigation accuracy and to achieve the required sensitivity.

Introduction to the special issue on the BeiDou navigation system

Abstract: China's BeiDou Navigation Satellite System (BDS) has evolved from a demonstration system (BDS-1) to a regional navigation satellite system (BDS-2) and has finally entered the phase of a global navigation system (BDS-3). In 2018, the BDS-3 implementation achieved historic milestones. A baseline constellation with 18 MEO satellites and one GEO satellite has been established. The BDS has the ability to provide fundamental positioning, navigation, and timing (PNT) services to global users. The current BDS features some distinctive design and unique service capabilities. First, the BDS provides a regional message communication service and a global short message communication service with 1000 and 40 Chinese characters at a time, respectively. Second, the BDS also provides a global search and rescue (SAR) service, a satellite-based augmentation service (SBAS), as well as a regional precise point positioning (PPP) service. This special issue of the Institute of Navigation's journal, NAVIGATION, provides a collection of papers presenting research achievements in the BDS over the last 2 years. It covers essential fields necessary to ensure the successful operation of BDS, such as constellation design, operational and control system design and construction, frequency and signal design, updated coordinate reference system and time system, satellite orbit determination, ionospheric model, and software receiver. Papers in this special issue present the development status of the BDS from several perspectives and introduce the main performance and progress to readers, which is helpful for researchers in the field of satellite navigation and beneficial to GNSS terminal manufacturers as well. The publication of the issue also provides an opportunity to promote users' understanding and applications of the BDS. We hope that readers find useful information in this issue, and we look forward to sharing our continued success in future BDS development.

Multi-satellite time-delay estimation for reliable high-resolution GNSS receivers

Abstract: Reliable estimation of position in time and space has become a key necessity in several technical applications like mobile navigation, precision farming or network synchronization. While the increasing amount of operating Global Navigation Satellite Systems (GNSS) offers diverse possibilities to receive GNSS signals worldwide and to determine position accurately, inter- and intrasystem interference has been identified as a problem of growing importance. The performance of receivers which track all in-view satellites individually degrades if mutual interference is not taken into account. Therefore, we consider the problem of joint signal parameter estimation. For scenarios where the signals of different satellites superimpose at the receiver a joint maximum likelihood estimator for all relevant signal parameters is derived. In order to keep the computation of the related likelihood function, and the determination of its maximum, feasible for a low-complexity receiver, an iterative Expectation-Maximization (EM) algorithm is applied. Simulations for different scenarios show that this approach is efficient in the estimation theoretic sense, and robust against interference that is caused by signals with known structure.

Comparison Between PS and SBAS InSAR Techniques in Monitoring Shallow Landslides

Abstract: The main aim of this study is to compare the two commonly used multi-temporal interferometric synthetic aperture radar (InSAR) techniques, i.e. permanent scatterers (PS) and small baseline subset (SBAS), in monitoring shallow landslides. PS and SBAS techniques have been applied to ascending and descending Sentinel-1 SAR data to measure the rate of surface deformation and the displacement time series in the Rovegliana area (NE Italian pre-Alps) from 2014 to 2019. As expected, PS results cover only urban areas, while those obtained by SBAS cover up to the 85% of the investigated area. Velocity maps obtained by the two techniques show that some sectors of the investigated slope are affected by active shallow landslides which threaten the stability of buildings, walls and road network. The comparison between ascending and descending velocity maps along the satellite line of sight reveals the presence of a horizontal component in the east–west direction which is consistent with the landslide kinematic. The analysis of the displacement time series shows that, in the case of linear deformation trends, PS and SBAS results are similar, whereas, in the case of high oscillations and non-linear behavior, SBAS technique can provide a better estimation of the displacements. Besides, SBAS provides smoother and less noisy displacement time series. However, both the techniques showed their high capability in monitoring the evolution of the landslides, which is crucial for the implementation of effective risk prevention and mitigation strategies. To deep investigate the differences between the two techniques, other geomatic methodologies, based on global navigation satellite system and terrestrial laser scanning, should be used.