• 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.22 no.2
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• pp.96-104
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• 2018

NOTAM is an announcement that is distributed to flight attendants with status information related to aviation. ICAO, the International Civilian Aviation Organization, recommends that a NOTAM service be provided for the SBAS service in order to use the SBAS signal-based access procedure. To comply with ICAO recommendation, KASS must provide NOTAM service to all aircraft landing using SBAS signal in order to provide APV-I SoL service. Therefore, it is necessary to develop KASS NOTAM system to provide KASS NOTAM service. In this paper, we analyzed the regulations related to NOTAM in Korea and abroad and analyzed the present state of NOTAM service in Korea. Based on this, we propose a method of providing KASS NOTAM service. We analyzed the NOTAM system of WAAS in the US and EGNOS in Europe and analyzed the main functional requirements of the KASS NOTAM system.

• Journal of Advanced Navigation Technology
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• v.27 no.5
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• pp.643-648
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• 2023

The Korea Augmentation Satellite System is an SBAS system being developed with the goal of providing SoL (Safety of Life) in accordance with ICAO (International Civil Aviation Organization) standards by December 2023. Monitoring the status of the system is essential for the continuous provision of KASS services, and a status monitoring tool should be developed for this purpose. The development of a status monitoring tool was divided into SYSRT (SYStem Real Time monitoring tool), SMSPP (Subsystem Monitoring Statistics tool for Post Processing) depending on the purpose. Tool development was completed through a series of procedures: requirements definition, design, development, and verification. To verify the status monitoring tool, the KASS system's real data (August 2023) were used to verify it, and the results were statistically analyzed to derive operating time and operating rate. It plans to use these tools to support continuous service provision for SoL service starting after this year.

• Journal of Positioning, Navigation, and Timing
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• v.12 no.4
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• pp.431-436
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• 2023

In order to provide continuous Korea Augmentation Satellite System (KASS) services, the operation organization should continuously and systematically perform operations, maintenance, and technical activities. All subsystems of KASS, all Line Replacement Units (LRUs), and Software Replacement Units (SWRUs) should be operated and maintained continuously. In order to effectively manage these activities, it is necessary to develop an Operation Management Tool (OMT). For this purpose, operation management, operation organization, and operation activities were defined. The defined requirements were divided into general, function, interface, and database for OMT development, and functions and decision-making procedures consisting of site/asset/trouble/work order/schedule management were designed. The OMT developed by reflecting the site and asset information as well as the design content met predefined requirements. The OMT will be actively used in actual KASS operation and will evolve by continuously reflecting the additional requirements of operators. Through this tool, KASS will support continuous service provision.

• Journal of Positioning, Navigation, and Timing
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• v.12 no.1
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• pp.23-35
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• 2023

Korea Augmentation Satellite System (KASS) is a satellite-based augmentation system (SBAS) that provides approach procedure with vertical guidance-I (APV-I) level corrections and integrity information to Korea territory. KASS is used to monitor navigation performance in real-time, and this paper introduces the design, implementation, and verification process of mission monitoring (MIMO) in KASS. MIMO was developed in compliance with the Minimum Operational Performance Standards of the Radio Technical Commission for Aeronautics for Global Positioning System (GPS)/SBAS airborne equipment. In this study, the MIMO system was verified by comparing and analyzing the outputs of reference tools. Additionally, the definition and derivation method of accuracy, integrity, continuity, and availability subject to MIMO were examined. The internal and external interfaces and functions were then designed and implemented. The GPS data pre-processing was minimized during the implementation to evaluate the navigation performance experienced by general users. Subsequently, tests and verification methods were used to compare the obtained results based on reference tools. The test was performed using the KASS dataset, which included GPS and SBAS observations. The decoding performance of the developed MIMO was identical to that of the reference tools. Additionally, the navigation performance was verified by confirming the similarity in trends. As MIMO is a component of KASS used for real-time monitoring of the navigation performance of SBAS, the KASS operator can identify whether an abnormality exists in the navigation performance in real-time. Moreover, the preliminary identification of the abnormal point during the post-processing of data can improve operational efficiency.

• Journal of Positioning, Navigation, and Timing
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• v.6 no.4
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• pp.181-194
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• 2017

In recent years, research has been actively conducted on the navigation in an indoor environment where Global Navigation Satellite System signals are unavailable. Among them, a study performed indoor navigation by integrating pseudolite carrier and Inertial Measurement Unit (IMU) sensor. However, in this case, there was no solution for the cycle slip occurring in the carrier. In another study, cycle slip detection and compensation were performed by integrating Global Positioning System (GPS) and IMU in an outdoor environment. However, in an indoor environment, cycle slip occurs more easily and frequently, and thus the occurrence of half cycle slip also increases. Accordingly, cycle slip detection based on 1 cycle unit has limitations. Therefore, in the present study, the aforementioned problems were resolved by performing indoor navigation through the integration of pseudolite and ultra-low-cost IMU embedded in a smartphone and by performing half cycle slip detection and compensation based on this. In addition, it was verified through the actual implementation of real-time navigation.

• Journal of Positioning, Navigation, and Timing
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• v.7 no.4
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• pp.295-305
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• 2018

Network RTK is a highly practical technology that can provide high positioning accuracy at levels between cm~dm regardless of user location in the network by extending the available range of RTK using reference station network. In particular, unlike other carrier-based positioning techniques such as PPP, users are able to acquire high-accuracy positions within a short initialization time of a few or tens of seconds, which increases its value as a future navigation system. However, corrections must be continuously received to maintain a high level of positioning accuracy, and when a time delay of more than 30 seconds occurs, the accuracy may be reduced to the code-based positioning level of meters. In case of SSR, which is currently in the process of standardization for PPP service, the corrections by each error source are transmitted in different transmission intervals, and the rate of change of each correction is transmitted together to compensate the time delay. Using these features of SSR correction is expected to reduce the performance degradation even if users do not receive the network RTK corrections for more than 30 seconds. In this paper, the simulation data were generated from 5 domestic reference stations in Gunwi, Yeongdoek, Daegu, Gimcheon, and Yecheon, and the network RTK and SSR corrections were generated for the corresponding data and applied to the simulation data from Cheongsong reference station, assumed as the user. As a result of the experiment assuming 30 seconds of missing data, the positioning performance compensating for time delay by SSR was analyzed to be horizontal RMS (about 5 cm) and vertical RMS (about 8 cm), and the 95% error was 8.7 cm horizontal and 1cm vertical. This is a significant amount when compared to the horizontal and vertical RMS of 0.3 cm and 0.6 cm, respectively, for Network RTK without time delay for the same data, but is considerably smaller compared to the 0.5 ~ 1 m accuracy level of DGPS or SBAS. Therefore, maintaining Network RTK mode using SSR rather than switching to code-based DGPS or SBAS mode due to failure to receive the network RTK corrections for 30 seconds is considered to be favorable in terms of maintaining position accuracy and recovering performance by quickly resolving the integer ambiguity when the communication channel is recovered.

• Journal of Cadastre & Land InformatiX
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• v.50 no.1
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• pp.107-123
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• 2020

With stabilization of the recent multi-GNSS infrastructure, and as multi-GNSS has been proven to be effective in improving the accuracy of the positioning performance in various industrial sectors. In this study, in view that SF(Single frequency) GNSS receivers are widely used due to the low costs, evaluate effectiveness of SF Real Time Point Positioning(SF-RT-PP) based on four multi-GNSS surveying methods with RTCM-SSR correction streams in static and kinematic modes, and also derive response challenges. Results of applying SSR correction streams, CNES presented good results compared to other SSR streams in 2D coordinate. Looking at the results of the SF-RT-PP surveying using SF signals from multi-GNSS, were able to identify the common cause of large deviations in the altitude components, as well as confirm the importance of signal bias correction according to combinations of different types of satellite signals and ionospheric delay compensation algorithm using undifferenced and uncombined observations. In addition, confirmed that the improvement of the infrastructure of Multi-GNSS allows SF-RT-SPP surveying with only one of the four GNSS satellites. In particular, in the case of code-based SF-RT-SPP measurements using SF signals from GPS satellites only, the difference in the application effect between broadcast ephemeris and SSR correction for satellite orbits/clocks was small, but in the case of ionospheric delay compensation, the use of SBAS correction information provided more than twice the accuracy compared to result of the Klobuchar model. With GPS and GLONASS, both the BDS and GALILEO constellations will be fully deployed in the end of 2020, and the greater benefits from the multi-GNSS integration can be expected. Specially, If RT-ionospheric correction services reflecting regional characteristics and SSR correction information reflecting atmospheric characteristics are carried out in real-time, expected that the utilization of SF-RT-PPP survey technology by multi-GNSS and various demands will be created in various industrial sectors.

• Journal of Advanced Navigation Technology
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• v.21 no.6
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• pp.601-607
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• 2017

This study performed fault test on global positoining system (GPS) carrier phase measurements, which is a preprocessing step to generate the positioning correction information based on the global navigation satellite system (GNSS) infrastructure. The existing carrier acceleration ramp step test (CARST) method affects the test result by using the mean value to eliminate the receiver clock error. In this regard, this study applied differencing and compared its results with those of the existing CARST. The fault simulation that applied artificial faults to the actual data found that the fault could be detected independently on each satellite when difference method was applied, and the single difference CARST and the double difference CARST produced similar results. The comparison with the existing method using actual data demonstrated the strengths and weaknesses of satellite and station single difference. Nevertheless, it is our understanding that it would require an additional analysis to determine whether the results were affected by the satellite or receiver clock error.