• 정보와 통신
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• 제10권11호
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• pp.74-84
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• 1993

Hyundai Electronics Industries Corp has developed a navigation system which automatically computes the current position and displays it on the map using GPS(Global Positioning System). This system has such features as follow : searching of destination by means of digital mapping, locating of the present position on the map and detecting of guidance timing through signals from the artificial satellites and vehicle's sensors, and having a few of functions as TV & VTR monitoring, tracing the route, displaying service information which include hotels, restaurants, entertainments, et al. This paper describes the operations and construction of this navigation system.

• 대한원격탐사학회지
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• 제33권6_1호
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• pp.993-1001
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• 2017

가뭄은 전 지구차원의 다방면에 걸쳐 피해를 주는 자연 재해이다. 21세기 들어 최근까지 다양한 위성관측 기기를 활용하여 다양한 가뭄의 유형을 모니터링 할 수 있게 되었는데, SMAP위성의 토양수분, GRACE 위성의 생태계 물 저장량, Terra & Aqua의 생태계 생산량과 증발산량 그리고 위성 강우 관측 등이 그 예이다. 이들 위성 자료의 분석을 통해 지역적 수자원 현황 및 가뭄과 이로 인한 (수)생태계 영향, 농업 등의 산업, 그리고 인간사회의 영향을 시공간적으로 파악할 수 있다. 가시광선부터 마이크로파까지 채널 (밴드)마다 관측할 수 있는 기상 및 환경 변수가 다르기 때문에 다양한 센서로부터 획득할 수 있는 원격탐사자료는 한반도 전역을 대상으로 가뭄에 대한 수자원 변화와 연관된 피해를 시공간적으로 파악하는 데에 상호 보완적이며 효과적인 수단이다. 따라서 이러한 위성자료들을 통해 국가 재난 대응 차원의 활용방안을 제안하고자 한다.

• Journal of Positioning, Navigation, and Timing
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• 제12권1호
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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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• 제12권4호
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• pp.359-367
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• 2023

In order to ensure the high-integrity of reference stations of satellite navigation system, cycle slip should be precisely monitored and compensated. In this paper, we proposed a cycle slip algorithm for the integrity monitoring of the reference stations. Unlike the legacy method using the Melbourne-Wübbena (MW) combination and ionosphere combination, the proposed algorithm is based on ionosphere combination only, which uses high precision carrier phase observations without pseudorange observations. Two independent and complementary ionosphere combinations, Ionospheric Negative (IN) and Ionospheric Positive (IP), were adopted to avoid insensitive cycle slip pairs. In addition, a second-order time difference was applied to the IN and IP combinations to minimize the influence of ionospheric and tropospheric delay even under severe atmosphere conditions. Then, the cycle slip was detected by the thresholds determined based on error propagation rules, and the cycle slip was identified through weighted least square method. The performance of the proposed cycle slip algorithm was validated with the 1 Hz dual-frequency carrier phase data collected under the difference levels of ionospheric activities. For this experiment, 15 insensitive cycle slip pairs were intentionally inserted into the raw carrier phase observations, which is difficult to be detected with the traditional cycle slip approach. The results indicate that the proposed approach can successfully detect and compensate all of the inserted cycle slip pairs regardless of ionospheric activity. As a consequence, the proposed cycle slip algorithm is confirmed to be suitable for the reference station where real time high-integrity monitoring is crucial.

• Journal of Positioning, Navigation, and Timing
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• 제9권1호
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• pp.1-6
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• 2020

The Chinese BeiDou Satellite Navigation System consists of three kinds of constellations: the geostationary Earth orbit (GEO), the inclined geosynchronous satellite orbit (IGSO), and the medium Earth orbit (MEO). The BeiDou has expanded its service coverage from regional to global. Recently, the BeiDou has been widely used in ionospheric total electron content (TEC) research. In this study, we analyzed the BeiDou signals for ionospheric TEC monitoring over Jeju Island in South Korea. The BeiDou GEO TEC showed a clear pattern of diurnal variations. In addition, we compared the TEC values from the BeiDou GEO, the BeiDou IGSO, GPS, and International GNSS Service (IGS) Global Ionosphere Maps (GIM). There was a difference of about 5 TEC units between the BeiDou GEO and the IGS GIM. This may be due to the altitude difference between the different navigation satellites.

• Journal of Positioning, Navigation, and Timing
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• 제11권4호
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• pp.269-277
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• 2022

In this paper, we overview the system development status of the national maritime precise point positioning-real-time kinematic (PPP-RTK) service in Korea, also known as the Precise POsitioning and INTegrity monitoring (POINT) system. The development of the POINT service began in 2020, and the open service is scheduled to start in 2025. The architecture of the POINT system is composed of three provider-side facilities-a reference station, monitoring station, and central control station-and one user-side receiver platform. Here, we propose the detailed functionality of each component considering unidirectional broadcasting of augmentation data. To meet the centimeter-level user positioning accuracy in maritime coverage, new reference stations were installed. Each reference station operates with a dual receiver and dual antenna to reduce the risk of malfunctioning, which can deteriorate the availability of the POINT service. The initial experimental results of a testbed from corrections generated from the testbed network, including newly installed reference stations, are presented. The results show that the horizontal and vertical accuracies satisfy 2.63 cm and 5.77 cm, respectively. For the purpose of (near) real-time broadcasting of POINT correction data, we designed a correction message format including satellite orbit, satellite clock, satellite signal bias, ionospheric delay, tropospheric delay, and coordinate transformation parameters. The (near) real-time experimental setup utilizing (near) real-time processing of testbed network data and the designed message format are proposed for future testing and verification of the system.

• Journal of Positioning, Navigation, and Timing
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• 제11권4호
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• pp.317-325
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• 2022

In this paper, we developed a single frequency-based RRAIM to monitor integrity of the UAM landing vertically in urban area with only low-cost single-frequency GPS receiver. Conventional dual-frequency RRAIM eliminates ionospheric delay through a combination of frequencies. In this study, ionospheric delay was directly modeled. Drift error of residual ionospheric delay is modeled using the previously studied result on ionospheric rates of change. To verify the performance of the proposed RRAIM algorithm, a simulation of vertical landing UAM in urban area was conducted. It was assumed that the protection level at the initial position was calculated through SBAS correction data. During vertical landing, integrity monitored by receiver alone without external correction data. In the 60 sec simulation, the protection level of the proposed RRAIM compared to the conventional RRAIM was calculated to be 140% due to the accumulated ionospheric delay error. Nevertheless, it was confirmed that the final vertical protection level meeting the requirements of LPV-200, which cannot be achieved with single frequency GPS receiver alone.

• 환경영향평가
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• 제9권2호
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• pp.119-126
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• 2000

Environmental monitoring system has been adopted and supplemented as inspection measures for the quantitative and qualitative changes of environmental impact assessment (EIA). Meanwhile it has been continuously pointed out that there is insufficient connection between environmental monitoring system and EIA. Often the agreed environmental impact assessment has not been fulfilled due to the argument of the cost, timing and situations of construction sites. Thus the purpose of this study is in search of the rationalized environmental monitoring system in order to harmonize the development and environmental conservation through the improvement of unreasonable aspects of the current EIA execution process. As to comply with the purpose, this research was carried out with three different but complimentary sources: environmental laws and regulations, foreign case studies of Japan, U.S.A. and Canada, and interviews with 73 experts. Finally, improved environmental monitoring system has been introduced reflecting the present process of EIA.

• 한국산학기술학회논문지
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• 제8권3호
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• pp.483-487
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• 2007

본 연구에서는 TFT-LCD Panel 생산한 후 Panel을 검사하는 공정에서 사용되는 Ti-Con 보드의 동작 상태를 실시간으로 모니터링하고 원격지에 있는 엔지니어에게 TCP/IP를 이용하여 고장 유무를 판별할 수 있는 데이터를 전송함으로써 신속한 대처가 가능할 뿐만 아니라 다중 프로세스가 가능하도록 제어할 수 있는 시스템을 개발하였다.

• Journal of Positioning, Navigation, and Timing
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• 제4권2호
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• pp.67-72
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• 2015

Power grid techniques are distributed over general power systems ranging from power stations to power transmission, power distribution, and users. To monitor and control the elements and performance of a power system in real time in the extensive area of power generation, power transmission, wide-area monitoring (WAM) and control techniques are required (Sattinger et al. 2007). Also, to efficiently operate a power grid, integrated techniques of information and communication technology are required for the application of communication network and relevant equipment, computing, and system control software. WAM should make a precise power grid measurement of more than once per cycle by time synchronization using GPS. By collecting the measurement values of a power grid from substations located at faraway regions through remote communication, the current status of the entire power grid system can be examined. However, for GPS that is used in general national industries, unexpected dangerous situations have occurred due to its deterioration and jamming. Currently, the power grid is based on a synchronization system using GPS. Thus, interruption of the time synchronization system of the power system due to the failure or abnormal condition of GPS would have enormous effects on each field such as economy, security, and the lives of the public due to the destruction of the synchronization system of the national power grid. Developed countries have an emergency substitute system in preparation for this abnormal situation of GPS. Therefore, in Korea, a system that is used to prepare for the interruption of GPS reception should also be established on a long-term basis; but prior to this, it is required that an evaluation technique for the time synchronization performance of a GPS receiver using an atomic clock within the power grid. In this study, a monitoring system of time synchronization based on GPS at a power grid was implemented, and the results were presented.