• Journal of Advanced Navigation Technology
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• v.26 no.6
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• pp.412-417
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• 2022

In this paper, multi-GNSS network RTK MAC correction generation software developed based on MATLAB GUI is introduced. The software was developed as a post-processing software based on simulation data to evaluate the feasibility of an algorithm for generating correction for multi-GNSS including GPS, GLONASS, and Galileo. As a result of software operation, network RTK correction for each system of multi-GNSS is output in MATLAB file format. In this paper, to evaluate the performance of the developed software, the residual error was analyzed after applying the correction generated through the software to the user. As a result of the analysis, it was confirmed that effective network RTK correction could be generated by confirming that the residual errors of users were maintained at 10 cm or less.

• Asia-pacific Journal of Multimedia Services Convergent with Art, Humanities, and Sociology
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• v.7 no.11
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• pp.933-940
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• 2017

The modern society is changing paradigm by the 4th industrial revolution. In these changes, the importance of geospatial information leading to the fusion and connection of persons and objects is increasing day by day. GNSS CORS(Continuously Operating Reference Station) plays a pivotal role in the geospatial information by providing basic data for surveying control points, mapping, navigation, geophysical research, and so on. On the other hand, the satellite surveying technologies are developing rapidly and it is necessary to investigate the status of the satellite surveying environment and search for future directions. In this study, the environment related to satellite survey by operation status of domestic and overseas CORS(Continuously Operating Reference Station) was tried to analyze. Through the research, The operation status of NGII and IGS CORS were presented. It was found that the availability ratio of multiple satellites to the CORS of NGII are lower than that of IGS CORS. Considering the improvement of positioning performance by using multiple GNSS, it is necessary to use multi-satellites in the future.

• Journal of Advanced Navigation Technology
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• v.20 no.5
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• pp.417-424
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• 2016

Russia recently began broadcasting the SDCM signal in order to provide SBAS service for the civil aviation in the Russian territory using its own geostationary satellites. The service coverage of the SDCM geostationary satellite, LUCH-5A and LUCH-5B, includes Korea peninsula, where the test signal from the pseudo random number (PRN) 140 is received. This paper shows that the position accuracy at the Chulwon GNSS site is improved to 0.8749 m (horizontal) and 0.9589 mm (vertical) by applying the received SDCM message to the RINEX data. Considering that the SDCM augments both GPS and GLONASS, the performance of multi-constellation SBAS was compared to that of GPS-only SBAS, and APV-I availability was improved by decreasing the protection level about 30 %. From the results, we can expect that the mult-constellation SBAS can contribute to the performance enhancement of the future KASS.

• Proceedings of the Korea Water Resources Association Conference
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• 2015.05a
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• pp.514-514
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• 2015

홍수 예측의 개선에 있어 정확한 공간 토양수분 정보는 필수적이다. 위성관측을 활용한 토양수분관측이 이루어지고 있으나 실제적 토양수분 상태와 정량적 차이가 크므로 편이보정을 통한 정량적 개선과정이 요구되는 실정이다. 따라서, 본 연구에서는 위성에서 관측한 AMSR2 토양수분과 지상관측 토양수분자료 및 다중회귀모형를 이용하여 토양수분자료를 정량적로 개선하였다. 공간 해상도가 10 km인 AMSR2 토양수분을 1 km로 상세화한 우리나라 전역의 토양수분 자료와 수자원관리종합정보시스템(WAMIS)에서 제공하는 강우관측소 556개 지점에서 관측한 강우자료, 후처리한 MODIS LST 자료, 증발산량 및 식생지수를 사용하였다. 2012년 7월부터 2013년까지 기상청 농업기상관측관서에서 관측하는 지점 중 사용 가능한 6개 토양수분관측소 자료에 대해 토양군별회귀계수를 산정하였다. 토양군별 다중회귀모형을 이용하여 편이보정한 토양수분자료는 전반적으로 과소추정되는 AMSR2 토양수분의 단점을 개선하여 위성관측 토양수분자료의 활용성을 개선하였다(Fig. 1).

• Proceedings of the Korea Water Resources Association Conference
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• 2016.05a
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• pp.601-601
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• 2016

글로벌 위성 기반의 강수량 관측에 대한 역사는 1979년에 Arkin의 의해 제안된 IR방법에 의해 위성으로 부터 강우자료를 유도하는 개념이 도입된 이후 1987년 해양에서의 비교적 정확한 강수량 추정이 가능한 다중 채널의 마이크로파(MW) 복사계를 이용한 방법으로 위성강수 추정에 대한 연구가 활발히 진행되었다. 이 후 두 IR과 MW를 혼합한 방법에서, 또다시 1997년 TRMM위성의 PR(Precpipitation Radar)의 레이더를 이용하는 방법, 그리고 2014년 GPM 핵심 위성(GPM Core Observatory)에 탑재된 Dual PR에 의한 방법으로 위성강수의 정확도를 매우 높여가고 있다. 전지구강수관측위성(GPM, Global Precipitation Measurement Mission) 사업은 미국우주항공국(NASA)과 일본우주항공국(JAXA)의 주도로 전 지구 규모의 강수관측을 목적으로 시작되었으며, 추가 파트너로 프랑스의 CNES(French Centre National d'?tudes Spatiales), 인도의 ISRO(Indian Space Research Organisation), 미국 NOAA, 그리고 유럽연합의 EUMETSAT(European Organisation for the Exploitation of Meteorological Satellites)가 참여하고 있다. 본 연구는 2014년 4월 발사된 GPM핵심 위성의 발사에 따라 제공되는 GPM 위성강우 자료의 정확도 평가를 목적으로 하고 있다. GPM 데이터는 Level-1에서 Level-3까지 다양한 데이터를 제공하고 있으며 본 연구에서는 Level-3의 IMERG 데이터를 이용하여 위성강우의 정확도를 평가하였다. IMERG 위성강우자료는 GPM 위성군의 모든 수동 MW 데이터를 조합하여 강우량을 추정하는 데이터이다. 자료의 시간적 범위는 2015년 8월 18일~8월 20일이고 공간적 범위는 한반도 영역으로 하였으며, 자료의 정확도 평가를 위한 지상계측자료는 기상청 ASOS(Automated Synoptic Observing System)의 강수량 자료를 이용하였다. 자료분석 결과 GPM에서 제공되는 IMERG 데이터의 공간적 분포는 그림 1과 같이 전라도 지역에 많은 강수가 분포하는 것을 확인할 수 있다. 이 기간 동안의 기상청 ASOS 관측 강수량 기록은 전국적으로 1순위가 고창군 25.5mm, 2순위가 부안군 21.9mm, 3순위가 정읍 및 영광군이 19.0mm로 위성으로부터 관측된 값과 지상계측값의 공간적 분포가 매우 유사한 경향을 보이는 것으로 분석되었다. 향후 위성강우 및 지상계측강우의 시계열적 정확도와 총강우량 등의 정확도 평가를 수행할 계획이다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.43 no.2
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• pp.141-148
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• 2015

This paper presents a sun-synchronous orbit design which effectuvely includes the requirements derived from spacecraft to ground station contact and spacecraft to target image accessibility. For this purpose, operation parameters of multiple spacecraft are defined as Contact Overlap, Contact Overlap Gap, Access Overlap, Access Overlap Gap. These parameters are used to form a Figure of Merit that reflects the operational requirements. The Figure of Merit is optimized to increase the efficiency of operating multiple spacecraft in constellation and is used to determine the operational orbit of each spacecraft that constitutes the constellation.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.36S no.6
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• pp.30-36
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• 1999

Jamming is an important factor in the military satellite communication system. In this paper, link capacity and jamming margin of the DS-CDMA(Direct Sequence-Code Division Multiple Access) military satellite communication system are analyzed and calculated under a multitone jamming. The analysis was performed with two types of transponders loaded on a geosynchronous satellite. Calculation methods for link capacity and jamming margin were obtained. The results of the analysis show that capacity of a transponder which does modulation/demodulation, decoding/encoding in addition to despreading/respeading is twice as much as that of a tranponder which does despreading /respreading only.

• Journal of Satellite, Information and Communications
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• v.5 no.2
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• pp.45-49
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• 2010

This paper presents the study on multi-beam large aperture antenna systems for a satellite payload. Multi-beam large antenna provides the universal communication and broadcasting services to personal portable terminals. The hybrid antenna composed of a large reflector and a feed array forms multi-beams. The feed cluster consists of a group of feed elements and each element should be optimized for the appropriate amplitude and phase. The optimization progress for amplitude and phase was performed by GO (Geometrical Optics) and PO (Physical Optics) method. The number of feed elements as well as the power level per element were also optimized to meet the required EIRP (Effective Isotropically Radiated Power). In conclusion, 30m-class reflector and twenty five elements for fifteen beams over Korean Peninsula were designed through the optimization process.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.38 no.6
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• pp.521-531
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• 2020

QZSS (Quasi-Zenith Satellite System) provides the CLAS (Centimeter Level Augmentation Service) through the satellite's L6 band. CLAS provides correction messages called C-SSR (Compact - State Space Representation) for GPS (Global Positioning System), Galileo and QZSS. In this study, CLAS messages were received by using the AsteRx4 of Septentrio which is a GPS receiver capable of receiving L6 bands, and the messages were decoded to acquire C-SSR. In addition, Multi-GNSS (Global Navigation Satellite System) Code-PPP (Precise Point Positioning) was developed to compensate for GNSS errors by using C-SSR to pseudo-range measurements of GPS, Galileo and QZSS. And non-linear least squares estimation was used to estimate the three-dimensional position of the receiver and the receiver time errors of the GNSS constellations. To evaluate the accuracy of the algorithms developed, static positioning was performed on TSK2 (Tsukuba), one of the IGS (International GNSS Service) sites, and kinematic positioning was performed while driving around the Ina River in Kawanishi. As a result, for the static positioning, the mean RMSE (Root Mean Square Error) for all data sets was 0.35 m in the horizontal direction ad 0.57 m in the vertical direction. And for the kinematic positioning, the accuracy was approximately 0.82 m in horizontal direction and 3.56 m in vertical direction compared o the RTK-FIX values of VRS.

• Journal of Satellite, Information and Communications
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• v.1 no.1
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• pp.20-25
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• 2006

The link of Geostationary Communication Satellite has transit delay and noise environments by physical distance. This situation exerts an influence on the degradation of baseband performance of Earth Station. Therefore, it is very important that degradation of baseband performance is grasped previously. This paper is presented that developed the simulator which can evaluate the baseband performance of earth station of a military satellite communication system during the current development. The simulator can mock delay on a satellite channel and bit errors without being used actual satellite links.