• Journal of Positioning, Navigation, and Timing
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• 제10권2호
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• pp.145-151
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• 2021

According to the Korea Augmentation Satellite System (KASS) system milestone, Site Acceptance Test (SAT) has three steps test until the end of the project. SAT#1 is the first time of SAT steps and verify the KASS Reference Station (KRS) and Sub System (S/S) for the monitoring and controllable. After the equipment and software were installed at the Mission Control Center (MCC) with Central Monitoring and Control Simulator (CMS) for the SAT#1, the 1:1 test was progressed when the KRS and S/S are ready to test. SAT#1 has a 10 steps test case and it was progressed each KRS sites. The test was finished throughout the real-time monitoring and the data collection including the data analysis all of the 7 KRS sites. Finally SAT#1 was completed on December 2020 with successfully.

• 한국항행학회논문지
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• 제27권6호
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• pp.782-787
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• 2023

KASS (korea augmentation satellite system) 시스템 통합 및 검증(IVQ; integration, verification, qualification) 활동은 시스템 및 하위시스템 요구사항 검증 활동으로 IART(inspection, analysis, review of design, test) 기반으로 상세설계 (CDR; critical design review) 이후 하위시스템 공장수락시험 (FAT; factory acceptance test)부터 현장수락시험 (SAT; site acceptance test) 그리고 시스템 통합 검증 시험 (TRR; test readiness review) 까지 수행하였다. FAT 단계의 활동은 개발된 장비를 테스트 플랫폼에 설치하고 각 장비별 인터페이스 검증과 통합운영국(KCS; kass control station)과의 연동시험을 통해 성능을 검증하였다. SAT 단계의 활동은 FAT 단계에서 검증된 KRS (kass reference station), KPS (kass processing station), KUS (kass uplink station), KCS를 운영 현장에 설치하고 검증하는 단계이며 개발 일정 및 여건을 고려하여 3단계로 구분하여 수행하였다. TRR 단계의 활동은 항공위성1호기에서 방송되는 SBAS (satellite based augmentation system) 메시지를 이용하여 SAT을 통해 검증된 장비를 FAT 단계에 수행했던 시험 항목과 추가 시험 항목 검증을 통해 전체 시스템에 대한 성능 검증을 완료하였다.

• Journal of Positioning, Navigation, and Timing
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• 제11권1호
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• pp.51-58
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• 2022

Korea Augmentation Satellite System (KASS) is a Satellite Based Augmentation System (SBAS) system under development in South Korea and aims to provide air navigation services after 2023. In order to provide reliable service, detailed design for the operation of this system is required. This paper proposes a detailed operation-based designs based on mission, architecture, operation definition of the system. For the stable operation of the system, an operation organization was designed and operation activities were classified in consideration of the architecture and function of the system. Detailed operation procedures were designed according to this classification and operation procedures related to the command and configuration of subsystem were verified on the Integration, Verification and Qualification (IVQ) platform for integrated testing and verification. The proposed operation concepts and procedures will be continuously confirmed and verified during verification, qualification and service preparation, and will be updated event after official KASS service.

• Journal of Positioning, Navigation, and Timing
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• 제7권4호
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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 Positioning, Navigation, and Timing
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• 제10권2호
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• pp.139-144
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• 2021

In this paper, we described configuration and construction of infrastructure for the KASS Reference Station (KRS), subsystem of Korea Augmentation Satellite System (KASS). KASS system consists of three subsystems(KRS, Mission Control Center (MCC), KASS Uplink Station (KUS)). One of these subsystems, KRS receives GNSS data for generating range error and integrity verification and sends to MCC. It is needed to antenna facilities for mounting GNSS antenna and shelter for operating KRS and infra equipment(power and network system, lightning and grounding system, fire extinguish) for operating KRS. For this reason, we have established the requirements for KRS infrastructure and constructed infrastructure for KRS to meet the requirements of KRS infrastructure.

• 한국항행학회논문지
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• 제24권4호
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• pp.273-279
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• 2020

한국형 SBAS (KASS)에서 기준국 사이트는 GPS/GEO 신호를 수집하고 감시하는 중요한 인프라 시설이다. SBAS 기준국은 상시 관측소보다 요구사항이 명확하고, 운영 단계에서 지속적인 유지보수가 필요하다. KASS 기준국 사이트 구축은 사이트 조사, 사이트 공사, 안테나 측지측량, 장비 설치 및 운영을 위한 준비가 필요하다. 사이트 조사는 사이트 가용 여부 및 시스템 성능 예측을 위한 단계이다. 기준국 사이트, 장비실 및 부대시설은 운영 기관이 사이트 요구 사항을 만족하도록 제공해야 한다. 기준국 안테나의 위치는 매우 중요한 정보로 측지측량을 통하여 정확도를 확보해야 한다. 정확한 위치의 안테나에서 측정된 측정치는 중앙처리국에 제공된다. 기준국의 정확한 위치는 향후 지속적인 위치 확인 및 업데이트를 수행해야한다. 기준국 사이트 구축이 완료 되면, 기준국 장비 설치 및 운영을 위한 업무를 수행한다. 본 논문에서는 7곳의 기준국 사이트의 구축 절차 및 결과를 제시하였다.

• International Journal of Aeronautical and Space Sciences
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• 제10권1호
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• pp.75-82
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• 2009

In this parer, we propose a new way of improving DGNSS service using combination of multiple SBAS information. Because SBAS uses Geostationary Earth Orbit (GEO) satellites, it has very large coverage but it can be unavailable in urban canyon because of visibility problem. R. Chen solved this problem by creating Virtual Reference Stations (VRS) using the SBAS signal [1]. VRS converts SBAS signal to RTCM signals corresponding its location, and broadcast the converted RTCM signals over the wireless internet. This method can solve the visibility problem cost effectively. Furthermore it can solve DGNSS coverage problem by creating just a transmitter instead of a reference station. Developing above method, this paper proposes the methods that integrate two or more SEAS signals into one RTCM signal and broadcast it. In Korea, MSAS signal is available even though it is not officially certified for Korean users. As a Korean own SBAS-like system, there is the internet-based KWTB (Korean WADGPS Test Bed) which we developed and released at ION GNSS 2006. As a result, virtually two different SBAS corrections are available in Korea. In this paper, we propose the integration methods for these two independent SBAS corrections and present the test results using the actual measurements from the two systems. We present the detailed algorithm for these two methods and analyze the features and performances of them. To verify the proposed methods, we conduct the experiment using the logged SBAS corrections from the two systems and the RINEX data logged at Dokdo monitoring station in Korea. The preliminary test results showed the improved performance compared to the results from two independent systems, which shows the potential of our proposed methods. In the future, the newly developed SBASs will be available and the places which can access the multiple SBAS signals will increase. At that time, the integration or combination methods of two or more SBASs will become more important. Our proposed methods can be one of the useful solutions for that. As an additional research, we need to extend this research to the system level integration such as the concept of the decentralized W ADGPS.

• Journal of Positioning, Navigation, and Timing
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• 제12권1호
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• pp.83-89
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• 2023

The Korea Augmentation Satellite System (KASS) system is a Satellite Based Augmentation System (SBAS) under development to provide APV-I SBAS service in the Republic of Korea. The KASS ground segment generates correction and integrity information for GPS measurements of KASS users using the accurate positions of KASS Reference Station (KRS) antenna phase centers. For this reason, the accuracy of KRS reference points through geodetic survey campaigns is one of the important factors for providing the KASS service in compliance with the required navigation performance. In order to obtain accurate positions, two geodetic survey campaigns were performed at several reference points, such as Mark, Center of Mast at Ground Level (CMGL), and Center of Hole in Top Plate (CHTP), of each KRS site using three different survey methods, the Virtual Reference Station (VRS), Flächen Korrektur Parameter (FKP), and raw data post-processing methods. By comparing and analyzing the results, the computed coordinates of the reference points were verified and Antenna Phase Center (APC) positions were calculated using KRS Antenna Reference Point (ARP) data, and the first KASS Site Acceptance Test (SAT#1) was performed successfully using the verified APC coordinates. After the first site survey activities, the KASS operators should maintain the coordinates with the required performance such that the overall KASS navigation performance commitment is guaranteed during the lifetime of 15 years. Therefore, the maintenance plan for the KRS antenna coordinates should be developed before the commissioning of KASS operation planned after 2023. Therefore, this paper presents a geodetic survey method selected for the maintenance activities and provides the rationale for using this method.

• 한국항행학회논문지
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• 제26권6호
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• pp.373-379
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• 2022

KASS (korea augmentation satellite system)는 국제민간항공기구 (ICAO; international civil aviation organization)의 항공통신 관련 국제표준권고 (SARPs Annex 10)에 따른 항공용 서비스 성능이 보장되어야 하는 한국형 SBAS (satellite based augmentation system) 이다. 목표 서비스 성능의 보장을 위해서는 운영 시스템이 안정적으로 동작하고 유지, 관리되어야 하며 이를 위해 유지보수 체계가 확립되어야 한다. 유지보수 관점에서 KASS 하위시스템을 교체유닛 단위로 정의하고 유지보수 조직, 유지보수 절차를 정의하였다. 또한, 유지보수 수행을 위한 교체유닛 단위의 유지보수 임무를 산출하였으며 산출된 임무가 앞서 정의된 교체유닛 단위를 충분히 포괄하는지 검증하였다. 본 연구를 통해 산출된 유지보수 임무는 2023년 말 본격적인 항공용 서비스 제공 전, 실 운영 준비과정에서 검증될 것이며 지속해서 업데이트될 것이다.

• Journal of Positioning, Navigation, and Timing
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• 제11권4호
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• pp.327-332
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• 2022

The Korea Augmentation Satellite System (KASS) is the Satellite-Based Augmentation System (SBAS) under development in Korea. KASS navigation service support navigation Safety of Life (SoL) service. KASS signal provides corrections to Global Positioning System (GPS) data received from KASS Reference Stations (KRS) and is broadcast form Geostationary Earth Orbiting (GEO) satellites to KASS users and is used by GPS/SBAS user equipment to improve the accuracy, availability, continuity and integrity of the navigation solution. Seven KRS's collect the satellite data and send them to the KASS Processing Stations (KPS) for the generation of the corrections and the monitoring the integrity. For performing its computation the KPS needs to know accurate and reliable KRS antennas coordinates. These coordinates are provided as configuration parameters to the KPS. This means that the reference frame in which the KPS work is the one represented by the set of coordinates provided as input. Therefore, the activity to maintain the accuracy of the KRS antenna coordinates is necessary, knowing that coordinates can evolve due to earth plates movements or earthquakes. In this paper, we analyzed the geodetic survey results for KRS antenna coordinates from Site Acceptance Test (SAT) #1 in December 2020 to August 2022. In the future, it is expected that these activities and planning for KRS coordinates maintenance will be produced and provided to KASS system operators for KPS configuration updates during the KASS lifetime of 15 years. Through these maintenance activities, it is expected that monitoring and analysis of unpredictable events such as earthquakes and seism will be possible in the future.