Evaluation of Orbit, Clock and Ionospheric Corrections from Five Currently Available SBAS L1 Services: Methodology and Analysis

Abstract

To meet the demands of civil aviation and other precise navigation applications, several satellite-based augmentation systems (SBASs) have been developed around the world, such as the Wide Area Augmentation System (WAAS) for North America, the European Geostationary Navigation Overlay Service (EGNOS) for Europe, the Multi-functional Satellite Augmentation System (MSAS) for Japan, the GPS (Global Positioning System) Aided GEO Augmented Navigation (GAGAN) for India, and the System for Differential Corrections and Monitoring (SDCM) for Russia. The SBASs broadcast messages to correct satellite orbit, clock, and ionosphere errors to augment the GPS positioning performance. In this paper, SBAS orbit, clock and ionospheric corrections are evaluated. Specifically, the orbit, clock and ionospheric corrections derived from SBAS messages are comprehensively evaluated using data collected from the above mentioned systems over 181 consective days. The evaluation indicates that the EGNOS outperforms other systems with signal-in-space range error (SISRE) at 0.645 m and ionospheric correction accuracy at 0.491 m, respectively. Meanwhile, the accuracy of SDCM is comparable to EGNOS with SISRE of 0.650 m and ionospheric correction accuracy of 0.523 m. For WAAS, the SISRE is 0.954 m and the accuracy of ionospheric correction is 0.505 m. The accuracies of the SBAS corrections from the MSAS and GAGAN systems, however, are significantly worse than those of others. The SISREs are 1.931 and 1.325 m and the accuracies of ionospheric corrections are 0.795 and 0.858 m, for MSAS and GAGAN, respectively. At the same time, GPS broadcast orbit, clock and ionospheric corrections are also evaluated. The results show that there are no significant improvements in the SISRE of the broadcast navigation data by applying SBAS corrections. On the other hand, the accuracy of SBAS ionospheric corrections is still much better than GPS broadcast ionospheric corrections, which could still be beneficial for single-frequency users.

Klobuchar, NeQuick G, and EGNOS Ionospheric Models for GPS/EGNOS Single-Frequency Positioning under 6–12 September 2017 Space Weather Events

“…A somewhat different genesis of creation, in relation to the global Klobuchar and NeQuick models, is characterised by the local ionosphere models used by SBAS (Satellite-Based Augmentation System) systems. The ionospheric delay in SBAS systems has been the subject of many previous scientific studies [33][34][35]. Thanks to the fact that these models are created in real time (updated every 5 min), they can be applied for safety-of-life applications such as aviation, where there is a need for a high integrity of data; thus, positioning based on information only from GPS/GLONASS (Global Positioning System/GLObal NAvigation Satellite System) systems [36] is not satisfactory for the aviation users.…”

An Enhanced Mapping Function with Ionospheric Varying Height

“…This is the simplest and most commonly used. One example is the broadcast model used in GPS [18], as shown in Equation (4). Later, Schaer [19] modified the SLM MF to approximate the extended slab model from the Jet Propulsion Laboratory (JPL) by scaling the zenith angle, as shown in Equation 5.…”

“…However, both satellite and receiver differential code biases (DCBs) adversely distort the GNSS-derived ionospheric observables for obtaining absolute TEC. To separate the DCBs from the TEC, ionospheric modeling is necessary [2][3][4].…”

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

“…The precise ionospheric delay of each user was required to analyze the results in the range domain. The leveled carrier phase measurement was utilized as the ground truth data when the residual errors were calculated [35,36]. For a continuous arc with no cycle slip, the integer ambiguity is constant.…”