• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.34 no.3
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• pp.299-308
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• 2016

Various space geodetic techniques have been developed for highly precise and cost-efficient positioning solutions. By correcting the physical phenomena near the earth’s surface, the positioning accuracy can be further improved. In this study, the vertical crustal deformation induced by the ocean tide loading was accurately estimated through GNSS absolute and relative positioning, respectively, and the tidal constituents of the results were then analyzed. In order to validate the processing accuracy, we calculated the amplitude of eight major tidal constituents from the results and compared them to the global ocean tide loading model FES2004. The experimental results showed that absolute positioning and positioning done every hour during the observation time of 2 hours, which yielded an outcome similar to the reference ocean tide loading model, were better approaches for extracting tide constituents than relative positioning. As a future study, a long-term GNSS data processing will be required in order to conduct more comprehensive analysis including an extended tidal component analysis.

• Proceedings of the Korean Society of Surveying, Geodesy, Photogrammetry, and Cartography Conference
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• 2010.04a
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• pp.103-105
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• 2010

우리나라는 지리적 메커니즘을 고려할 때 지각판 거동에 의한 지진발생 가능성을 가지고 있으며, 최근들어 지진 횟수가 증가됨에 따라 지진에 대한 우려와 관심이 커지고 있다. 이에 본 연구에서는 지진 발생 가능성이 높은 단층지역에 위치하고 있는 양산 상시관측소로부터 수신한 GPS 자료를 정밀절대측위 방법으로 처리하고, 양산지역의 지각변동량을 계산하였다. 연구결과 양산지역은 방위각 약 $131^{\circ}$의 4cm/year 속도로 이동하고 있음을 알 수 있었으며, 이러한 결과는 양산단층지역에 대한 지구 물리 해석의 기초자료로 활용이 가능할 것으로 기대된다.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.30 no.5
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• pp.477-484
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• 2012

Recently, as earthquake is more frequently taking place around the world due to diastrophism, the importance of diastrophism and disaster detection is becoming more important. In this study, to analyze the interpretation of seismic displacement by the Japanese earthquake in March, 2011, and monitor the diastrophism of plates in Japan and surrounding Eurasia, Pacific, and Philippines before and after the earthquake, the observational data from IGS observatories in Japan and Asian regions were processed by precise point positioning. The displacement was biggest in MIZU, which was the closest to the epicenter, and the earthquake-affected region was in inverse proportion to the distance from the epicenter. The result of calculating the diastrophism speed before and after the earthquake, based on precise point positioning of IGS observatories located in the 4 plates around Japan, showed that the displacement speed changed and different plates showed different results. The comparison with the plate fate model allowed to analyze the change in diastrophism by earthquake, and to understand the characteristics of the displacement of the plates around Japan. Later, a continuous diastrophism monitoring based on GPS is needed for earthquake prediction and diastrophism research, and the data gained by continuous GPS-based monitoring of diastrophism will be fully used as basic data for relevant research and earthquake disaster management.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.17 no.2
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• pp.145-152
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• 1999

JPL(Jet Propulsion Laboratory) has been routinely produced the precise GPS ephemeris and clock's correction parameter using data collected from globally distributed permanent GPS tracking stations, and has been offering the automated GPS data analysis(Precise Point Positioning： PPP) service by using them. In this study, after investigating the potential capacity of JPL's PPP service, the coordinates computation of the GPS base station by this service were investigated. For this, the dual frequency P codes data of 24 hours were observed from continuously operating four reference stations in USA. sent to the JPL's main computer through E-mail and/or ftp, and then were processed by Gipsy/Oasis-II (GOA-II) software with the precise GPS transmitter parameters. Centimeter-level positioning results were available to obtain in X, Y, Z geocentric rectangular coordinate system.

• 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 Korea Institute of Information and Communication Engineering
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• v.20 no.1
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• pp.142-152
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• 2016

GPS is not able to be used for indoor positioning and currently most of techniques emerging to overcome the limit of GPS utilize private wireless networks. However, these methods require high costs for installation and maintenance, and they are inappropriate to be used in the place where precise positioning is needed as in indoor parking lots. This paper proposes a vehicular indoor positioning method based on QR-code recognition. The method gets an absolute coordinate through QR-code scanning, and obtain the location (an relative coordinate) of a black-box camera using the tilt and roll angle correction through affine transformation, scale transformation, and trigonometric function. Using these information of an absolute coordinate and an relative one, the precise position of a car is estimated. As a result, average error of 13.79cm is achieved and it corresponds to just 27.6% error rate in contrast to 50cm error of the recent technique based on wireless networks.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.19 no.10
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• pp.2321-2330
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• 2015

A variety of studies for indoor positioning are now being in progress due to the limit of GPS that becomes obsolete in the room. However, most of them are based on private wireless networks and the situation is difficult to commercialize them since they are expensive in terms of installation and maintenance costs, non-real-time, and not accurate. This paper applies the mark recognition algorithm used in existing augmented reality applications to the indoor vehicle positioning application. It installs floor marks on the ground, performs the perspective transformation on it and decodes the internal data of the mark and, as a result, it obtains an absolute coordinate. Through the geometric analysis, it obtains current position (relative coordinates) of a vehicle away from the mark and the heading direction of the vehicle. The experiment results show that when installing the marks every 5 meter, an error under about 30 cm occurred. In addition, it is also shown that the mark recognition rate is 43.2% of 20 frames per second at the vehicle speed of 20km/h. Thus, it is thought that this idea is commercially valuable.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.37 no.3
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• pp.101-108
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• 2019

Due to recent improvements in computer processing speed and image processing technology, researches are being actively carried out to combine information from camera with existing GNSS (Global Navigation Satellite System) and dead reckoning. In this study, developed a vision-based positioning assistant algorithm to estimate the distance to the object from stereo images. In addition, GNSS/on-board vehicle sensor/vision based positioning algorithm is developed by combining vision based positioning algorithm with existing positioning algorithm. For the performance analysis, the velocity calculated from the actual driving test was used for the navigation solution correction, simulation tests were performed to analyse the effects of velocity precision. As a result of analysis, it is confirmed that about 4% of position accuracy is improved when vision information is added compared to existing GNSS/on-board based positioning algorithm.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.37 no.1
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• pp.1-7
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• 2019

In this study, we estimated the tropospheric delay of GNSS (Global Navigation Satellite System) signals during passing through the atmosphere in relation to weather and seasonal factors. For this purpose, we chose four CORS (Continuously Operating Reference Station) stations from inland (CCHJ and PYCH) and on the coast (GEOM and CHJU). A total of 48 days for each station (one set of data for each week) were downloaded from the NGII (National Geographic Information Institute) and processed it using the scientific GNSS software. The average tropospheric delays in winter are less than 2,400 mm, which is about 200 mm less than those in summer. The estimated tropospheric delay shows a similar pattern from all stations except the absolute bias in magnitude, while a large delay was observed for the station located on the coast. In addition, the delay during the day was relatively stable in winter, and the average tropospheric delay was strongly related to the orthometric height. The inland stations have tropospheric delays by the precipitation rather than humidity due to dry weather and difference in temperature. On the contrary, it was primarily caused by the humidity on the sea. The correlation between temperature and water vapor pressure is 0.9 or larger for all stations, and the tropospheric delay showed a high linear relationship with temperature. It is necessary to analyze the GNSS data with higher temporal resolution (e.g. all RINEX data of the year) to improve the stability and reliability of the correlation results.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.23 no.3
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• pp.283-292
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• 2005

After USA removed the Selective Availability (SA), Global Positioning System (GPS) has monopolized the world market and other countries have been depended on GPS, absolutely. So the other countries, Russia, European Community (EC) and Japan, which apprehend to monopolize in technical and strategic parts, are developing the next generation GNSS including GLONASS Galileo and JRANS. And the countries are planning to provide the another GNSS. This research has focused on the next generation GNSS system based on GPS and Galileo system with developing a GNSS simulation software, named as GlMS2005, which generates and analyzes satellite constellation and measurements. Based on the software, a variety of simulation tests have been carried out to recognize limits of GPS-only system and potential benefits of integrated GPS/Galileo positioning in terms of satellite geometry strength and solution accuracy.