• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.26 no.2
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• pp.157-164
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• 2008

GPS baseline analysis is a mathematical procedure which estimates a baseline vector from carrier-phase double-differenced observations. Least squares technique is generally applied for the processing and integer ambiguities in the observations should be resolved to obtain maximum accuracy of the solution. In GPS control surveying, after assembling the baseline solutions into a network, adjustment is performed to derive final coordinate sets of unknown points. This paper deals with details of GPS baseline analysis for the $2^{nd}$ order national geodetic network adjustment. After reviewing GPS campaigns carried out by National Geographic Information Institute (NGII) and their observations. technical issues and considerations for the GPS baseline analysis are presented with emphasis of selecting the processing strategies and software. Finally, the analyzed results will be evaluated by examining the close of figures formed by joining the processed baseline vectors.

• Journal of Korean Society for Geospatial Information Science
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• v.13 no.1 s.31
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• pp.3-10
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• 2005

This study attempts to measure effectively three dimensional deformation in road slopes using digital close-range photographs. After the still video images were acquired respectively on the same multi-station geometric configuration in two epoches, photo-triangulation was rallied out respectively by conventional standard bundle adjustment and free-net bundle adjustment and the computed results were compared with those of geodetic method by total station. Three dimensional coordinates and deformation amounts were able to be derived with the RMSE of sub-millimeter and the relative accuracy of $1/30,000{\sim}1/35,000$. It was shown that free-net bundle adjustment is about 13% higher than standard bundle adjustment in the accuracy of photo-triangulation. It was ascertained that the free-net technique is able to promote fast and accurate deformation surveying without the necessity of geodetic control survey in complicated industrial sites.

• Journal of Astronomy and Space Sciences
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• v.23 no.4
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• pp.337-344
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• 2006

KVN simulation, which is focused on evaluating the impacts of KVN to geodetic VLBI network, was performed. The KVN is under construction with three radio telescopes VLBI system for radio astronomy and space geodesy. To distinguish the impacts of KVN on global and local scale networks, we designed two different sizes of VLBI networks, namely, KVN-Asia and KVN-Pacific. While the former consisted of Far East Asia region VLBI stations, the latter consisted of pacific region VLBT stations. The primary purpose of our simulation is quantitative evaluation of KVN impacts before and after the participation of KVN in the previous two virtual networks. We selected two different sets of parameters to be estimated in the simulation as indices of evaluating estimation precision: station coordinates and EOPs. The station coordinates are evaluating index for KVN-Asia and the EOPs are another evaluating index for KVN-Pacific. From the simulation results of comparisons between evaluating indexes, 50% and 20% of maximum improvements for KVN-Asia and KVN-Pacific were anticipated respectively. We expect that the space geodetic use of KVN will be focused on the several promising research fields which are proposed through the simulation results.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.27 no.1
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• pp.713-722
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• 2009

Gravity measurement can determine the earth gravitational field, also is the fundamental to the research of earth gravitational field, geodesy and geodynamic, vertical movement of the crust, geoid surface, sea level and climate etc. Recently, National Geographic Information Institute (NGII) introduced FG-5 absolute gravity meter in order to lay a foundation for establishment of Absolute Gravity Network, and furthermore NGII plan to construct about 1,200 multi dimensional and function Unified Control Points(UCP) in nationwide. It will play an important role in development of high accuracy geoid model in South Korea. This paper explains the fundamental theory and method of relative gravity measurement, surveys the relative gravity of 21 stations using latest Scintrex CG-5 relative gravimeter. In addition, it calculates gravity values, compare and analysis gravity survey results using datum-free adjustment and weighted constraint adjustment. The results indicate show that datum-free and weighted constraint adjustment methods are available to determine high accuracy gravity achievement, datum-free method is more advantage than weighted constraint adjustment.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.25 no.3
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• pp.207-213
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• 2007

For several years, although the demand of high accuracy kinematic positing using multiple bases has been increased, most of the commercial GPS processing softwares can provide the single-baseline solutions only. Thus, we studied the methods to improve the accuracy of the kinematic positioning using the network configuration based on the several single-baseline solutions. As discussed in this study, the positioning accuracy as well as the network stability is improved by introducing the geodetic network adjustment theories into the kinematic positioning application. Three different methods to remove the rank-deficiency, RLESS, BLIMPBE and SCLESS, are analyzed in this study. The 3D RMS error has been improved from 3.5cm(max) to 2.1cm using the network-based kinematic positioning, and it is desired to choose BLIMPBE and SCLESS depending on the accuracy of the base stations.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.5 no.2
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• pp.12-23
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• 1987

This paper deals with the analysis and adjustment computation for the Korean 1st order levelling data obtained by the National Geography Institute from 1974 to 1986. An evaluation of the accuracy of level lines using forward/back discrepancies and adjustment residuals has been carried out. A general assessment of the network in the light of current standards with other countries is discussed. The results of this study show that systematic errors are relatively high but the accuracy of the primary levelling is good enough within the limitation of precision levelling according to International Association of Geodesy(IAG) Resolution, and therefore it is concluded that this levelling will satisfy the present mapping and engineering survey.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.16 no.1
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• pp.51-58
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• 1998

The goal of this study is to propose a precision improvement scheme for long baseline determination based on the use of IGS ephemeris and different cutoff angles. It is also to present the adjustment results of ’96 Korea GPS fiducial network. In order to obtain more accurate coordinates in precise geodetic surveying, the revision of specification is necessary for the field operation and procedure of baseline processing.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.7 no.2
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• pp.27-34
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• 1989

Geodetic control networks have been used for more than 200 years by peculiar national system, both to establish the size and shape of the earth, and to determine the positions of points on its surface. Junction schemes for the densified geodetic network are proposed to the case whether the accuracy of existing network is known or unknown, in this paper. The concepts of adjustment, under the condition of partial $X^TX$＝min., is applied to densification system. Moreover, the technique of epoch analysis, which is often used in small deformation survey net, is introduced to the national control network for unstable point detection.

• Bulletin of the Korean Space Science Society
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• 2010.04a
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• pp.37.2-37.2
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• 2010

GPS 관측자료를 이용하여 최근 발생한 칠레지진에 의한 지각의 변위를 결정하고 결과를 분석하였다. 고정밀 측지용 이중주파수 GPS 수신기 및 안테나가 장착된 관측소의 자료를 처리하면 수mm 정밀도로 관측소의 위치를 결정할 수 있으며, 수년간의 관측자료가 누적되면 연간 mm급의 움직임도 관측할 수 있어 판운동이나 지진, 단층연구 등에 널리 활용되고 있다. 이번 2010년 2월 27일 칠레 중서부에서 발생한 지진은 인근 지역을 30 cm 이상 움직였을 것으로 예상되며 8.8의 대형 지진규모와 많은 인명 및 재산피해를 유발시켜 학계뿐만 아니라 일반 언론에도 많은 주목을 받고 있다. 이 연구에서는 지진이 발생한 지역 부근에 위치한 국제 GPS 기준망의 GPS 관측자료를 처리하여 지진 발생 전후의 변위를 산출하고 분석하였다. 자료처리를 위해 Bernese GPS S/W 5.0을 사용하였고 24시간단위 자료에 대해 이중차분방법과 단독정밀측위방법을 사용하였다. 또한 지진이 발생 도중의 변위를 관찰하기 위해 이동측위방법을 사용하여 30초마다의 움직임을 계산하였다.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.27 no.6
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• pp.699-710
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• 2009

If a country has her geoid model, it could be determine accurate orthometric height because the geoid model could provide continuous equi-gravity potential surface. And it is possible to improve the coordinates accuracy of national control points through geodetic network adjustment considering geoidal heights. This study aims to find the best way to develop geoid model in Philippines which have similar topographic conditions as like Malaysia and Indonesia in Eastsouth asia. So, in this study, it is surveyed the general theories of geoid determination and development cases of geoid model in Asia and it is computed that the geoidal heights and gravity anomalies by spherical harmonic analysis using EGM2008, the latest earth geopotential model. The results show that first, the development of gravimetric geoid model based on airborne gravimetry is needed and second, about 200 GPS surveying data at national benchmark is needed. It is concluded that it is the most reasonable way to develop the hybrid geoid model through fitting geometric geoid by GPS/leveling data to gravimetric geoid. Also, it is proposed that four band spherical Fast fourier transformation(FFT) method for evaluation of Stokes integration and remove and restore technique using EGM2008 and SRTM for calculation of gravimetric geoid model and least square collocation algorithm for calculation of hybrid geoid model.