• The Journal of the Korea institute of electronic communication sciences
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• v.9 no.2
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• pp.195-202
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• 2014

The Global Positioning System (GPS), which has various military and commercial applications, is designed to estimate the location of the specific user or object. In order to accurately estimate the location, GPS requires at least four satellite signals. The GPS receiver operates on extremely low signal-to-noise ratio (SNR) environment and it may suffer from various interference signals with the extremely high power. In this paper, we introduce a blind adaptive receiver based on the modified despreader, which suppress interference signals and detect GPS signals of interest without requiring explicit angle-of-arrival (AOA) information. We, also, provide the mathematical analysis for the signal-to-interference and noise ratio (SINR) of the modified despeader beamformer output. A representative computer simulation example is presented to illustrate the interference suppression performance of the considered GPS receiver and mathematical analysis of the SINR.

• Journal of Navigation and Port Research
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• v.26 no.3
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• pp.303-310
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• 2002

Nowadays, the combined land navigation system using GPS(Global Positioning System) and DR(Deduced Reckoning), etc. has been used. Although GPS is popular with the land navigation system, this is not useful for the kinematic positioning of the vehicles in the urban canyon because of its few satellites. Thus, this study deals with the kinematic positioning of the vehicles with the combined GPS/GLONASS(GLObal Navigation Satellite System) to compliment the drawbacks of GPS. So the kinematic positioning of the vehicles can be performed constantly by the combined GPS/GLONASS based on the high acquisition rate of data with the help of GLONASS despite of many obstacles and few satellites tracked in the test sites. Consequently, the combined GPS/GLONASS can be applicable to the control of traffic flow and the effective management of read system.

• Journal of Satellite, Information and Communications
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• v.7 no.2
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• pp.104-109
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• 2012

Currently, GPS(Global Positioning System) is used to find user location information. However, in some cases, especially in urban environments, we receive unreliable location information deu to multipath fading. In order to resolve this problem, we propose a closely coupled positioning technique where GPS signal is combined with QZSS signal. Also we proposed and analyze a combining algorithm of GNSS and Wi-Fi signals to get closely coupled location information by referring AP information. Finally, this paper proposes a combined GPS/QZSS/Wi-Fi navigation algorithm to improve navigation performance, and it is verified by testing of car deriving according to availability and accuracy standard.

• Journal of Satellite, Information and Communications
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• v.10 no.3
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• pp.38-43
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• 2015

This paper describes a GPS signal generator that can generate multiple satellite signals in real time at the RF level. It realizes the verified software algorithm on a FPGA. The algorithm models orbits and environmental errors such as ionospheric and tropospheric multipath. The position of a simulated receiver is one of simulation parameters. The hardware which consists of a digital logic board and an analog board can generate 16 simulated satellites signals at the same time. The users can generate spoofing signals and jamming signals as well as satellite signals by using the windows-based control software. In addition, the software provides GIS-based simulation scenarios editing tools. We verified the generator by using commercial receivers. As an application, we configured generators as indoor positioning systems and tested them in a building. To improve the accuracy of indoor systems is our further study.

• Journal of Satellite, Information and Communications
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• v.8 no.1
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• pp.14-22
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• 2013

GPS radio occultation is a remote sensing technique probing atmospheric properties based on the fact that GPS signal is refracted and delayed by atmosphere. The FORMOSAT-3/COSMIC mission jointly developed by the USA and Taiwan is providing about 2500 occultation soundings a day on the near real-time basis. The Korean KOMPSAT-5/AOPOD system is preparing to launch for monitoring troposphere and ionosphere using a dual frequency GPS receiver and the antenna for occultation data acquisition. In this paper, we examine the methods for signal processing and the geometry analysis for GPS radio occultation, and look into the retrieval techniques for the temperature and humidity of troposphere and the electron density and scintillation of ionosphere. Using these atmospheric properties, we aim to derive the strategies for applying GPS radio occultation to space weather, for example, ionospheric TEC(total electron content) analysis for earthquake monitoring and the Open API(application programming interface) development for more effective data service.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.19 no.1
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• pp.1-8
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• 2001

The aim of this study is to know the GPS absolute positioning accuracy after discontinuing of Selective Availability (SA). The GPS satellite clock errors and the observation station coordinates were calculated using GPS C/A code pseudorange and compared with the JPL precise ephemerides and the previous known coordinates. As the results, the correction or the GPS clock errors in SA-on is about $\pm$40m but in SA-off $\pm$2m. The 95% probable errors for the measurements in SA-on are about $\pm$65m but in SA-off $\pm$10m in X, Y and SA-off $\pm$15m in Z.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.22 no.1
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• pp.73-80
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• 2004

The purpose of this study is the GCP/DEM estimations through satellite stereo image interpretation using GPS. We carried out GPS observation fixing first order control points and GPS permanent stations. Comparing static surveying and kinematic surveying, we analysed the surveying methods for GCP and DEM estimations. As the results, considering SPOT image spatial resolution, the DEM can be made through satellite stereo image interpretation.

• Proceedings of the Korea Information Processing Society Conference
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• 2001.10b
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• pp.1179-1182
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• 2001

본 논문에서는 차량합법시스템에서 위치정확도 향상을 위한 방법으로 GPS/DR 통합시스템을 사용하여 DLM(Dynamic Linear Model) 알고리즘을 적용한 개선된 통합필터를 제안하였다. GPS/DR 통합 시스템의 성능을 개선하기 위해서는 DR 센서의 오류요소를 정확히 모델링 하여야 한다. GPS 로부터 위치를 계산하기 위해서는 적어도 3개 이상의 가시위성이 필요하다. 그러나 도심지에서는 고층빌딩이나 가로수 등에 의한 장애물로 인해서 3개 이상의 가시위성을 확보하기가 힘든 경우가 많다. 본 논문에서는 가시위성의 확보가 힘든 고층 빌딩이나 가로수길 등에서도 우수한 성능을 보이는 GPS 의사거리 및 의사거리율 정보를 이용하는 CPS/DR 통합 DLM 필터를 이용하여 성능을 개선시키는 방법을 제시한다.

• Bulletin of the Korean Space Science Society
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• 2003.10a
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• pp.107-107
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• 2003

GPS Receiver는 위성에 위치 정보와 시간 정보등을 제공하고 navigation을 관리하며 이에 관련된 signal을 processing하는 역할을 한다. 2005년에 발사 예정인 KOMPSAT-2 위성에는 Alcatel에서 제작된 Topstar 3000이 사용된다. Topstar 3000은 RF 부분과 digital 처리부분으로 구성된 GPS core부분과 MLD-STD_1553, DC-DC converter, 그리고 Ovened-controlled Oscillator(OCXO)부분으로 구성되는 option module 부분으로 구성되어 있다. 본 논문에서는 GPS Signal Simulator로 KOMPSAT-2의 실제 궤도를 구현해서 Sun-Point Mode와 Earth-Point Mode 등 여러가지 Mode 에서 GPS Receiver의 시간, 위치, 속도 정보의 정확성에 대한 성능이 분석된다.

• Journal of Advanced Navigation Technology
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• v.14 no.5
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• pp.610-617
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• 2010

This paper analyzes the characteristics of abnormal broadcast GPS ephemeris by comparing distances between the receiver and the satellites. Effects of abnormal ephemeris on receiver's position estimate are closely related with range errors caused by variations of satellite positions. In more detail each range error depends on the satellite position error and the line of sight vector. Based on the fact, the ephemeris parameters are classified into three types depending on the size, the shape, and the shape of the satellite orbit to analyze the fault characteristics. The effects of satellite position errors caused by the three type s of parameters on the receiver's position estimate are analyze d in detail.