• Journal of Positioning, Navigation, and Timing
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• v.7 no.4
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• pp.245-253
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• 2018

The current SBAS service does not provide a method to integrate multiple SBAS corrections. This paper proposes a positioning method to effectively integrate multiple SBAS and multiple GNSS. In the method, the final position is obtained by the weighted sum of the positions obtained from the combination of GNSS and SBAS. Since each position is independently computed and combined using flexible weights, it has a simple structure that can easily cope with various environments. In order to verify the operation and performance of the proposed method, raw measurements of GNSS and SBAS were collected using commercial receivers. The experiments using real signals show that the combined use of two SBAS corrections was more accurate by 0.05~0.4m(2dRMS) than using only one SBAS correction. To improve the position accuracy, this paper considered the integration of multi-GNSS and multi-SBAS, which was not found in other existing studies. The proposed method is expected to be a core technology for designing multi-GNSS navigation receivers considering multi-SBAS corrections. The importance of the method will be increased as KPS and KASS also available in near future.

• Journal of Advanced Navigation Technology
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• v.23 no.3
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• pp.237-244
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• 2019

Since SBAS provides users with GNSS orbit, clock, and ionospheric corrections and integrity, the more precise positioning is possible. As the SBAS service area is expanded due to the development of the SBAS and the installation of the additional ground stations, there is a region where two or more SBAS messages can be received. However, the research on multi-constellation SBAS selection method has not carried out. In this study, we compared the result of positioning accuracy after applying the SBAS correction selected by using WAAS priority, EGNOS priority, or error covariance comparison method to LEO satellites in the regions where WAAS and EGNOS signals are transmitted simultaneously. When using WAAS priority method, 3D orbit error is smallest at 2.57 m. The covariance comparison method is outperform at the center of the overlap region far from each WAAS and EGNOS stations. In the eastern region near the EGNOS stations, the 3D orbit errors using EGNOS priority method is 8% smaller than the errors using the WAAS priority method.

• Journal of Positioning, Navigation, and Timing
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• v.5 no.4
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• pp.181-191
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• 2016

A Satellite Based Augmentation System (SBAS) provides differential correction and integrity information through geostationary satellite to users in order to reduce Global Navigation Satellite System (GNSS)-related errors such as ionospheric delay and tropospheric delay, and satellite orbit and clock errors and calculate a protection level of the calculated location. A SBAS is a system, which has been set as an international standard by the International Civilian Aviation Organization (ICAO) to be utilized for safe operation of aircrafts. Currently, the Wide Area Augmentation System (WAAS) in the USA, the European Geostationary Navigation Overlay Service (EGNOS) in Europe, MTSAT Satellite Augmentation System (MSAS) in Japan, and GPS-Aided Geo Augmented Navigation (GAGAN) are operated. The System for Differential Correction and Monitoring (SDCM) in Russia is now under construction and testing. All SBASs that are currently under operation including the WAAS in the USA provide correction and integrity information about the Global Positioning System (GPS) whereas the SDCM in Russia that started SBAS-related test services in Russia in recent years provides correction and integrity information about not only the GPS but also the GLONASS. Currently, LUCH-5A(PRN 140), LUCH-5B(PRN 125), and LUCH-5V(PRN 141) are assigned and used as geostationary satellites for the SDCM. Among them, PRN 140 satellite is now broadcasting SBAS test messages for SDCM test services. In particular, since messages broadcast by PRN 140 satellite are received in Korea as well, performance analysis on GPS/GLONASS Multi-Constellation SBAS using the SDCM can be possible. The present paper generated correction and integrity information about GPS and GLONASS using SDCM messages broadcast by the PRN 140 satellite, and performed analysis on GPS/GLONASS Multi-Constellation SBAS performance and APV-I availability by applying GPS and GLONASS observation data received from multiple reference stations, which were operated in the National Geographic Information Institute (NGII) for performance analysis on GPS/GLONASS Multi-Constellation SBAS according to user locations inside South Korea utilizing the above-calculated information.

• Korean Journal of Remote Sensing
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• v.26 no.2
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• pp.143-151
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• 2010

We carried out studies on InSAR techniques for time-series deformation monitoring using multi-temporal SAR. The PSInSAR method using permanent scatterer is much more complicate than the SBAS because it includes many non-linear equation due to the input of wrapped phase. It is conformed the PS algorithm is very sensitive to even PSC selection. On the other hand, the SBAS method using interferogram of small baseline subset is simple but sensitive to the accuracy of unwrapped phase. The SBAS is better method for expecting not significant unwrapping error while PSInSAR is more proper method for expecting local deformation within very limited area. We used 51 ERS-1/2 SAR data during 1992-2000 over Las Vegas, USA for the comparison between PSInSAR and SBAS. Both PSInSAR and SBAS show similar ground deformation value although local deformation seems to be detected in the PSInSAR method only.

• Journal of Advanced Navigation Technology
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• v.13 no.2
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• pp.178-186
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• 2009

SBAS(Satellite Based Augmentation System) provides GNSS satellite orbit and clock corrections for positioning accuracy improvement of GNSS users. In this paper, the accuracy of SBAS satellite orbit and clock corrections were analyzed by comparing with the IGS(International GNSS Service) precise ephemeris. The GPS antenna phase center offsets and the P1-C1 bias are considered for the analysis. The correction data of the US WAAS and the Japanese MSAS were analyzed. The analysis results showed that the SBAS satellite orbit and clock corrections are highly correlated. The correction data accuracy depends on the SBAS ground network size and orbit trajectories.

• Journal of Positioning, Navigation, and Timing
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• v.13 no.1
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• pp.25-34
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• 2024

The Satellite Based Augmentation System (SBAS) improves the accuracy and reliability of user positioning by transmitting the error correction and integrity information of the global navigation satellite system signal from geostationary satellites in real time. For this reason, SBAS was designed for aircraft operations and approach procedures and is now in operational or development stages in many countries. Time has passed since the construction of SBAS and many changes have occurred in the composition of the monitoring stations and the geostationary satellites. These changes have been investigated and the current operation and development status of SBAS globally are surveyed. The development and test schedules for the transition to dual frequency multi-constellation, an important topic in SBAS, are discussed.

• Korean Journal of Remote Sensing
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• v.30 no.6
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• pp.719-730
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• 2014

Small BAseline Subset (SBAS) technique using multi master interferograms can be effective to detect surface deformation in forest area. In this paper, The analysis reveals area of 2-dimension surface deformation at Seguam Island in Aleutian Arc., Alaska. We acquired ERS-1/2 data from track 201 and 473 datasets on Seguam Island from 1992 to 2008. This study analyze surface deformation applying Differential Interferometry Synthetic Aperture Radar (DInSAR) and SBAS time series method using two adjacent tracks. As a results, it was calculated that subsidence -1~2 cm in LOS direction and - 2~3 cm in vertical direction. The horizontal direction was repeated contraction and expansion. The observation of 2-dimension displacements explained the volcanic activity on Seguam island. Also, it is believed to be used for basic data to estimate movements of magma source.

• Journal of Positioning, Navigation, and Timing
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• v.7 no.4
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• pp.267-275
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• 2018

The reference stations in a satellite-based augmentation system (SBAS) collect raw data from global navigation satellite system (GNSS) to generate correction and integrity information. The multipath signals degrade GNSS raw data quality and have adverse effects on the SBAS performance. The currently operating SBASs (WAAS and EGNOS, etc.) survey existing commercial equipment to perform multipath assessment around the antennas. For the multi-path assessment, signal power of GNSS and multipath at the MEDLL receiver of NovAtel were estimated and the results were replicated by a ratio of signal power estimated at NovAtel Multipath Assessment Tool (MAT). However, the same experiment environment used in existing systems cannot be configured in reference stations in Korean augmentation satellite system (KASS) due to the discontinued model of MAT and MEDLL receivers used in the existing systems. This paper proposes a test environment for multipath assessment around the antennas in KASS Multipath Assessment Tool (K-MAT) for multipath assessment. K-MAT estimates a multipath error contained in the code pseudorange using linear combination between the measurements and replicates the results through polar plot and histogram for multipath assessment using the estimated values.

• Journal of Advanced Navigation Technology
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• v.17 no.4
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• pp.396-403
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• 2013

Recently, GNSS users can utilize various navigation satellite thanks to GPS modernization, renewal of GLONASS, and development of Galileo and Beidou. And availability performance of users is expected to be improved because these new navigation satellites transmit L5 signal as well as L1 signal, and users can directly estimate the ionospheric delays. In accordance with these changes existing Satellite Based Augmentation System (SBAS) which considers only GPS L1 signal is being developed to support dual frequency and multi-constellation GNSS users. This paper describes the main features of dual-frequency, multi-constellation SBAS algorithms and estimates the performance in Korean region by simulation.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.22 no.1
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• pp.15-21
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• 2014

Modern aircraft air navigation has been changed from the conventional air navigation aid to utilizing Global Navigation Satellite System. For the air navigation of fast moving aircraft, GNSS required extremely high accuracy and reliability. This study reviews the basic concept of Satellite Based Augmentation System which is discussed in the International Working Group of International Civil Aviation Organization and status of some SBAS leading State's case. In addition to that, a progress of SBAS development and implementation in the Republic of Korea was reviewed with pointing out of general hurdles and counter measures.