• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.1
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• pp.14-19
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• 2020

This paper proposes a precise drone-positioning technique using a differential global positioning system (DGPS). The proposed system consists of a reference station for error correction data production, and a mobile station (a drone), which is the target for real-time positioning. The precise coordinates of the reference station were acquired by post-processing of received satellite data together with the reference station location data provided by government infrastructure. For the system's implementation, low-cost commercial GPS receivers were used. Furthermore, a Zigbee transmitter/receiver pair was used to wirelessly send control signals and error correction data, making the whole system affordable for personal use. To validate the system, a drone-tracking experiment was conducted. The results show that the average real-time position error is less than 0.8 m.

• 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.

• Spatial Information Research
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• v.13 no.3 s.34
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• pp.283-296
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• 2005

Nowadays, Global Navigation Satellite System(GNSS) which is the new concept of positioning system has been developed because of satisfaction human's intelligent desire and rapid science development. GNSS which is represented by GPS provides 3-Dimension positioning information not expensively in whenever, wherever. The industry of positioning information has extending civil market widely as well as military market. So GNSS is running the role of society infra structure including car and airborne navigation, civil engineering, GIS resource, telematics and LBS, and so on. As USA removes the SA(Selective Availability), GPS has monopolizing the market and other countries have been depended on GPS, absolutely. In this paper, the author developed the software for analysis of influence using next generation, Galileo system. The local analysis was performed according to positioning mode. And GPS/Galileo combined system can implement positioning in the worst mask environment like urban cannon.

• Proceedings of the Korean Society of Surveying, Geodesy, Photogrammetry, and Cartography Conference
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• 2010.04a
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• pp.169-171
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• 2010

The goal of this study is to evaluate the performance of different solution types(a GPS-only, a GLONASS-only, and a GNSS solution) on GNSS positioning modes which are point positioning and relative positioning(DGNSS-, Static-, and Kinematic-solutions). I started with GNSS sites of seoul metropolitan government's RTK network which providing combined GPS/GLONASS observations : Gangseo(GANS), Dobong(DBON). The positioning accuracy of different solution types on positining modes are compared. Considering the compared results of all cases, can find not only the difference of the performance between the GNSS solution and the GPS-only solution is very small, but also the GLONASS-only solution is not far from the other solution types taking into consideration that GLONASS system is not (yet) a complete system.

• Journal of Astronomy and Space Sciences
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• v.27 no.2
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• pp.173-180
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• 2010

As a preparatory study for Global Positioning System-Very Long Baseline Interferometry (GPS-VLBI) hybrid system, we examined if VLBI type observation of the GPS signal is realizable through a test experiment. The test experiment was performed between Kashima and Koganei, Japan, with 110 km baseline. The GPS L1 and L2 signals were received by commercial GPS antennas, down-converted to video-band signals by specially developed GPS down converters, and then sampled by VLBI samplers. The sampled GPS data were recorded as ordinary VLBI data by VLBI recorders. The sampling frequency was 64 MHz and the observation time was 1 minute. The recorded data were correlated by a VLBI correlator. From correlation results, we simultaneously obtained correlation fringes from all 8 satellites above a cut-off elevation which was set to 15 degree. 87.5% of L1 fringes and 12.5% of L2 fringes acquired the Signal to Noise Ratios which are sufficient to achieve the group delay precision of 0.1nsec that is typical in current geodetic VLBI. This result shows that VLBI type observation of GPS satellites will be readily realized in future GPS-VLBI hybrid system.

• Journal of Astronomy and Space Sciences
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• v.28 no.1
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• pp.55-62
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• 2011

The precise orbit determination (POD) of low earth orbiter (LEO) has complied with its required positioning accuracy by the double-differencing of observations between International GNSS Service (IGS) and LEO to eliminate the common clock error of the global positioning system (GPS) satellites and receiver. Using this method, we also have achieved the 1 m positioning accuracy of Korea Multi-Purpose Satellite (KOMPSAT)-2. However double-differencing POD has huge load of processing the global network of lots of ground stations because LEO turns around the Earth with rapid velocity. And both the centimeter accuracy and the near real time (NRT) processing have been needed in the LEO POD applications--atmospheric sounding or urgent image processing--as well as the surveying. An alternative to differential GPS for high accuracy NRT POD is precise point positioning (PPP) to use measurements from one satellite receiver only, to replace the broadcast navigation message with precise post processed values from IGS, and to have phase measurements of dual frequency GPS receiver. PPP can obtain positioning accuracy comparable to that of differential positioning. KOMPSAT-5 has a precise dual frequency GPS flight receiver (integrated GPS and occultation receiver, IGOR) to satisfy the accuracy requirements of 20 cm positioning accuracy for highly precise synthetic aperture radar image processing and to collect GPS radio occultation measurements for atmospheric sounding. In this paper we obtained about 3-5 cm positioning accuracies using the real GPS data of the Gravity Recover and Climate Experiment (GRACE) satellites loaded the Blackjack receiver, a predecessor of IGOR. And it is important to reduce the latency of orbit determination processing in the NRT POD. This latency is determined as the volume of GPS measurements. Thus changing the sampling intervals, we show their latency to able to reduce without the precision degradation as the assessment of their precision.

• Journal of Advanced Navigation Technology
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• v.14 no.6
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• pp.783-790
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• 2010

For safety navigation of ships at sea, ships monitor their location obtained from Global Positioning Satellite System (GNSS). In this study, we computed near-real-time positions of a ship at sea using GPS Precise Point Positioning (PPP) technique and analyzed precision of the near-real-time positions. We conducted ship borne GPS observations in the south sea of Korea. To process the GPS data using PPP technique, GIPSY-OASIS (GPS Inferred Positioning System-Orbit Analysis and Simulation Software) developed by the Jet Propulsion Laboratory was used. Antenna phase center variations, ocean tidal loading displacements, and azimuthal gradients of the atmosphere were corrected or estimated as standard procedures of high-precision GIPSY-OASIS data processing. As a result, the precisions of near-real-time positions was ~1cm.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.38 no.5
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• pp.401-406
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• 2020

Continuously monitoring of Horizontal and Vertical movements in vulnerable areas due to earthquakes and volcanic activities is vital. These geohazard activities are the result of a slow deformation rate at the tectonic plate boundaries. The recent development of GPS (Global Positioning System) technology has made it possible to attain a millimeter level changes in the Earth's crust. This study used continuously observed GPS data at the flank of Ol Doinyo Lengai volcanic Mountain to determine crustal motion caused by impinging volcano from mantle convention. We analyzed 8 GPS observed from June 2016 to Dec 2019 using a well-documented Global Kalman Filter GAMIT/GLOBK software. The resulting velocity from GAMIT/GLOBK analysis was then used to compute the relative motion of our study area with respect to Nubia plate. Our analysis discovered a minor motion of less than 5mm/year in both horizontal and vertical components.

• Proceedings of the Korean Society of Computer Information Conference
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• 2017.07a
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• pp.119-120
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• 2017

최신 스마트폰은 GPS(Global Positioning System) 신호를 이용하여 비교적 정확한 위치정보를 제공한다. 그래서 GPS를 이용한 다양한 실외용 위치기반서비스 앱이 개발되고 있다. 그러나 GPS를 이용하면 비교적 많은 건전지 에너지가 소모되어 사용자에게 큰 불편을 준다. 본 논문은 지도정보와 에너지 소모가 적은 센서를 이용하여 건전지를 절약하는 방안을 제안한다.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• v.2
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• pp.431-434
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• 2006

현재 사용되는 디지털 신호처리 방식의 GPS(Global Positioning System) 수신기는 최소의 RF 블록만을 이용하여 모든 디지털 신호 처리를 소프트웨어로 수행하고 있다. 소프트웨어 GPS수신기의 장점으로는 디지털 신호처리 과정이 모두 소프트웨어로 구현되어 있기 때문에 새로운 구현 방식이나 알고리즘을 적용할 시, 하드웨어 변경은 필요가 없게 되고, 소프트웨어 재설계만으로 가능하다. GPS 수신기의 Tracking module 성능은 DLL discriminator function과 FLL discriminator function의 Algorithm에 의해서 영향을 받게 된다. DLL discriminator function algorithm에는 dot-product 와 normalized dot-product 방법 등이 있으며, FLL discriminator function algorithm에는 sign(dot)(cross)-product 와 cross-product 그리고 ATAN 방법이 있다. 이러한 discriminator function들은 algorithm에 따라 input error에 대한 discriminator의 출력 값을 일정한 범위에서의 차이를 나타내게 되면서 ranging accuracy에서 차이가 나타나게 된다. 본 논문에서는 Nordnav 소프트웨어 GPS 수신기를 이용하여 DLL discriminator algorithm과 FLL discriminator algorithm의 성능을 비교, 분석을 하고 Tracking accuracy, sensibility, 그리고 multipath rejection에 대해서 알아보고자 한다.