• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.27 no.4
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• pp.461-467
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• 2009

Relative positioning technique by GPS that can obtain the high positioning accuracy has been used for generation of high precision positioning with elimination or the reduction of the common errors. This paper gives some algorithms for RTK and considers the filter to estimate the positioning information and integer ambiguities at each epoch in the whole algorithms. The extended kalman filter has been employed to estimate the state parameters and the modified LAMBDA to resolve the integer ambiguities. The data processing was performed by GPS single frequency and dual frequency in short baseline. The verification procedure of these positioning compared with results from Bernese 5.0 software. We presented some statistic values on positioning errors and the rates of integer ambiguity resolution.

• Korean Journal of Geomatics
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• v.5 no.1
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• pp.43-49
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• 2005

It is well known that GPS technique can be used for high accuracy leveling positioning if a precise geoid model is available to use at a surveying point. In this study, KOGD2003 geoid model was developed in and around Korean peninsula and this geoid model could be achieved by combining GPS/leveling data with the formerly developed KOGD2002. To this end, the software for orthometric height obtaining and geodetic datum transformation has been implemented with the visual C++ language, what we called GPS-GeoL v.1.0. In order to evaluate the performance and the accuracy of the software, GPS field tests were carried out in the Korean second-order leveling network over Chollabukdo area. Results of the tests have shown that the mean value of the differences between outputs of the software developed in this research and officially announced orthometric heights by NGII (National Geographic Information Institute) was 0.0221 m and also those of RMS was 0.0332 m. Therefore, it was possible to conclude that the KOGD2003 and GPS-GeoL v.1.0 software could be used to determine orthometric heights for civil construction field applications with cm-level accuracy.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.30 no.6_2
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• pp.673-680
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• 2012

Long-term GPS data analysis was performed in order to analyze the seasonal variation of tropospheric delay and the success rate of the ambiguity resolution. For this analysis, a total of 57 stations including 10 IGS stations in East Asia were processed together with double-differenced observables using Bernese GPS Software V5.0. The time span for this study ranges from 2002.0 to 2012.5 (10.5 years). The average baseline length is 339.0 km and the maximum reaches up to 2,000 km. The analysis is focused on two things: the annual variation of the tropospheric delay and the ambiguity resolution rate. The tropospheric delay is closely related to the weather condition, especially relative humidity, therefore it was estimated that the maximum would be in summer, while reaching its minimum in winter with the apparent seasonal variations. On the contrary, however, the success rate of the ambiguity resolution shows the opposite pattern: its maximum was in winter and minimum in summer. The fact seems to be induced by the surrounding conditions; that is, the trees thick with leaves near the GPS antenna interfere with GPS signals in summer. This seems to confirm partly that there is a distinct trend in the decreasing success rate since 2006 because the trees are growing every year. It is necessary to eliminate the factors that degrade the GPS quality and the tropospheric modeling for Korea needs to be studied further.

• Proceedings of the Korean Society of Surveying, Geodesy, Photogrammetry, and Cartography Conference
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• 2006.04a
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• pp.119-124
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• 2006

The world which based on knowledge and information is changing significantly. In the various knowledge and information, the importance of GSIS has increased for efficient application and management of country. The Geomatics has made a change rapidly, observation methods have improved too. The existing acquisition of Geoinformation depend on aerial photogtaphs, but new technology Jike application of high resolution satellite images. SAR and LiDAR, is the fastest. especially, LiDAR surveying is most advanced active observation technology and Geoinfomtation is acquired by reflection of its laser pulse. In this study. the position accuracy of extracted building from LiDAR was evaluated by GPS surveying, then each data was made comparison between LiDAR's and GPS's data. After processing. the result of this study will be suggested basic data about application.

• Proceedings of the KSRS Conference
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• 2002.10a
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• pp.548-552
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• 2002

The necessity of a short period of software development with lower cost came out. The reason of making the component based development is that it can improve the software development , productivity maintenance , and software quality innovatively. Following these advantages of component based application development methods, we found the COM based components effective to Window platform in the satellite surveying. In this paper, we can obtain many precious engineering experiences. Software system development and maintenance will take much shorter time with higher reusability if satellite surveying system is constructed with component extraction proposed by us.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.27 no.5
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• pp.565-574
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• 2009

The water vapor weighted vertically mean temperature(Tm) models, which were developed by the consideration of seasonal characteristics over the Korea, was used in the retrieval of precipitable water vapor (PWV) from GPS data which were observed at four GPS permanent stations. Since the weighted mean temperature relates to the water vapor pressure and temperature profile at a site, the accuracy of water vapor information which were estimated from GPS tropospheric wet delay is proportional to the accuracy of the weighted mean temperature. The adaption of Korean seasonal weighted mean temperature model, as an alternative to other formulae which are suggested from other nation, provides an improvement in the accuracy of the GPS PWV estimation. Therefore, it can be concluded that the seasonally appropriate weighted mean temperature model, which is used to convert actual zenith wet delay (ZWD) to the PWV, can be more reduced the relative biases of PWV estimated from GPS signal delays in the troposphere than other annual model, so that it would be useful for GPS PWV estimation with high accuracy.

• Proceedings of the Korean Society of Surveying, Geodesy, Photogrammetry, and Cartography Conference
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• 2004.04a
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• pp.9-14
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• 2004

In this study, we analyzed that the geomagnetic storms in the end of October 2003 influenced a positioning of GPS permanent stations. The data that observed in total 23 permanent GPS stations are used, and did a precisely analysis every hour with GIPSY-OASIS II software to produced ITRF2000 coordinates of each stations. After that we analyzed and compared the ITRF2000 coordinates calculated every hour with public ITRF2000 results of each stations. As a result of this study, the increases of positioning errors showed well when geomagnetic storms happened and the maximum error reached about 0.80m.

• Proceedings of the Korean Society of Surveying, Geodesy, Photogrammetry, and Cartography Conference
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• 2007.04a
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• pp.77-80
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• 2007

In this paper GPS data for the period from January 2002 to June 2004 (910 days) were analyzed to quantitatively investigate the plate deformation patterns and distributions in the Korean peninsula. The GPS network is composed of 45 permanent GPS stations. The daily data were analyzed using the GAMIT/GLOBK software and the precise orbits generated by the International GNSS Service (IGS). The research result make it possible to understand the tendency of crustal movement in and around the Korean peninsula, which have an effect on the occurrence of earthquake.

• Proceedings of the Korean Society of Surveying, Geodesy, Photogrammetry, and Cartography Conference
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• 2007.04a
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• pp.37-42
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• 2007

A network of MAC type was constructed in the Gyeonggi-do area to analyze the usefulness and validity of the Network RTK-GPS. Six sites were selected to conduct GPS observation for 24 hours, and by determining the ITRF of each site, coordinates were determined in connection with IGS network. Then check points which were established in Gimpo area were observed at least 7 times by Network RTK at 20 secs of retrieval intervals. The result showed high accuracy in the difference between the coordinates determined immediately by the in-field network survey and the current performance was 1-2cm. Its biggest benefit is the expanded range of survey and efficiency of practice. In summary, it is proved that a network survey has the accuracy, scalability and efficiency and it is expected that the network survey will contribute to the cadastral survey.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.31 no.6_2
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• pp.539-547
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• 2013

This research is suggesting the most effective positioning method for GPS based positioning when no GPS reference point is available in the neighborhood. For this purpose, we carried out positioning of the IGS realtime observatories in Australia in various conditions. According to the research, we were certainly assured the one reference point with a short baseline length is more effective for differential positioning than multiple reference points with a long baseline distance beyond 1,000km and suggested the precise point positioning based positioning method can be an excellent substitute when no reference point is available around an unknown point. The research result may be used as the basic data for accurate positioning in poor reference point environments, especially in Antarctica.