• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.38 no.6
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• pp.561-571
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• 2020

Seven techniques widely used in the geodetic transformations have been reviewed and compared to figure out their theoretical characteristics. A series of numerical tests were performed about four data sets. This was followed by result analyses in terms of transformation residuals and accuracies together with some hypothesis testings based on the student-t distribution to confirm the statistical significance of the techniques. In the case of the transformation between the geodetic frames implemented in the same system, no statistical significance was revealed in the results of the 3D transformation techniques, even if the testing area becomes large as the Asia-Oceania continent. Among the 2D transformations, it was possible for the NTv2 grid modeling technique to deliver improved transformation accuracy. Finally, it was possible from the results analyzed in this study to propose the Helmert transformation to geodetic control points and the NTv2 technique to the 2D spatial data transformation of the geodetic systems.

• Journal of Korean Society for Geospatial Information Science
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• v.16 no.3
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• pp.79-85
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• 2008

This study aims to derive a practical coordinate transformation method for the existing geographic information database. After analyzing the status and problems of existing 1/1,000 digital base map and GIS application database, the transformation parameters are estimated and the accuracy of the transformation is determined based on the transformed coordinates. We analyzed the accuracy of a transformation using the published national transformation coefficients as well as the estimated local transformation coefficients using national and urban control points in a study area. In addition, the 1/1,000 digital base map from aerial triangulation is compared with respect to the coordinates of urban control points. Based on the comparison, the biases on the national control points which were used at the time of digital map generation was analyzed. Then, the accuracy of transformed coordinates based on the world geodetic system using local transformation coefficients estimated from urban control points are determined. We also analyzed the transformation accuracy of underground infrastructure database using the same transformation method as the case of 1/1,000 digital base map. Through this study, it was found that the estimation of transformation coefficients by Molodensky-Badekas using urban control points was suitable for a local government. Furthermore, it was obvious that the accuracy of a 2-dimensional affine transformation was comparable to that of 7 parameter transformation for a local area. Applying the coordinate transformation and bias correction, we could transform GIS application database which was built by an offset surveying based on digital base map within the transformation accuracy of 10 cm. Therefore, it was judged that there will not be a big problem on the transformation of the GIS DB to the world geodetic system.

• Proceedings of the Korean Society of Surveying, Geodesy, Photogrammetry, and Cartography Conference
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• 2006.04a
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• pp.53-58
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• 2006

Although the uninhabitable islands are part of national property, those are not systematically managed and controlled in Korea. In this study, the positioning standards for uninhabitable islands are suggested with proper surveying methods. To establish the standards, the current status on managing the uninhabitable islands in foreign countries are investigated and analyzed. It was found that it is necessary to establish the ocean geodetic network based on a sound and systematic plan. In Korea, the ocean geodetic network can be established by combining the National control point and territorial sea control points. We suggested that one or two third or fourth control points are required to be established in total of 2,679 islands with connection to the 47and 249 first and second-order control points. It is expected that this network will provide ground control points for aerial and satellite images for large scale ocean mapping. In addition, close cooperation among the related departments such as Ministry of Construction & Transportation, National Geographic Information Institute, Ministry of Government Administration and Home Affairs, Ministry of Maritime Affairs and Fisheries, and Ministry of Environment is necessary for successful management on uninhabitable islands.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.7 no.2
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• pp.35-43
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• 1989

The improvements of highly accurate and dense control networks are major requirements to carry out numerical surveying and a large scale mapping for cadastral renovation. In the most conventional photogrammetric solutions, adjusted control coordinates have been applied to block triangulations. However, this study, imploying real data and those of simulated as well, contributes to a simultaneously combined adjustment. It also contains such photogrammetric as photocoordinates and geodetic observations like distances, angles and hight differences. Its purpose is to introduce the improved results, despite it is not sufficient for the ground network. In addition, through the detection of gross error, more precise observational data can be selected for the better adjustment. All in all, the result of this study can be summarized as follows : First, even if the ground control points are not sufficient nor existed at all, the combination of pbotogrammetric and geodetic observations are improved its accuracy. Secondly, the case #2 is more accurate than that of #3, and the case #7 comes into close to that of #6.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.6 no.2
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• pp.19-27
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• 1988

In determining the horizontal positions, economic, speedy, and accurate analytical adjustment methods have studied and developed for a long time. From now on, the adjustment methods using both angles and distances are expected because the development of more precise instruments, E.D.M, and electronic total station provide us with more advantages than the conventional measurement system. The objective of this paper is to study the characteristics of triangulation, trilateration, and combination method due to change of the weight factor of angles, distances, azimuthes, and control point coordinates of combined geodetic network. The results of this study show that combined method is more accurate and effective than other methods in case of combined geodetic network as the other simple networks.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.17 no.4
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• pp.403-410
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• 1999

Mark point(Donghaksan) of Korean geodetic datum in Suwon could not be intervisible because of the development of the surroundings, so we were in a situation that we should establish new mark point and decide azimuth of the new mark point. Getting out of the intervisibility between control stations, refraction error and effect of illumination in urban area, our research team decided new azimuth of Suwon Geodetic Datum by GPS surveying for accuracy and economical efficiency. First we corrected and supplemented the specification on the decision of azimuth in accordance with our situation based on the study of foreign studies by using GPS, and we determined and analyzed the accuracy of the new azimuth through organizing and observing the GPS network.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.13 no.1
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• pp.151-159
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• 1993

In conjunction with a vertical network. horizontal geodetic control points provide the basic framework for topographic mapping and legal survey. The design of such networks as well as the technical means for obtaining their coordinates have been changed in time, and therefore Korea National Geographic Institute has planned and observed the precise geodetic network since 1975. The aim of this study is to investigate the systematic distortions of the precise geodetic network in Korea implementing by the simultaneous adjustment. The results show that there are large discrepancies between adjusted and public coordinates in Chun-nam and Kyung-buk areas. The coordinate discrepancies are mainly due to the non-rigorous adjustment method and the disregard of the orientation unknown of the first direction for some blocks.

• Journal of Astronomy and Space Sciences
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• v.30 no.4
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• pp.269-277
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• 2013

In this study, we present results of precise orbital geodetic parameter estimation using satellite laser ranging (SLR) observations for the International Laser Ranging Service (ILRS) associate analysis center (AAC). Using normal point observations of LAGEOS-1, LAGEOS-2, ETALON-1, and ETALON-2 in SLR consolidated laser ranging data format, the NASA/GSFC GEODYN II and SOLVE software programs were utilized for precise orbit determination (POD) and finding solutions of a terrestrial reference frame (TRF) and Earth orientation parameters (EOPs). For POD, a weekly-based orbit determination strategy was employed to process SLR observations taken from 20 weeks in 2013. For solutions of TRF and EOPs, loosely constrained scheme was used to integrate POD results of four geodetic SLR satellites. The coordinates of 11 ILRS core sites were determined and daily polar motion and polar motion rates were estimated. The root mean square (RMS) value of post-fit residuals was used for orbit quality assessment, and both the stability of TRF and the precision of EOPs by external comparison were analyzed for verification of our solutions. Results of post-fit residuals show that the RMS of the orbits of LAGEOS-1 and LAGEOS-2 are 1.20 and 1.12 cm, and those of ETALON-1 and ETALON-2 are 1.02 and 1.11 cm, respectively. The stability analysis of TRF shows that the mean value of 3D stability of the coordinates of 11 ILRS core sites is 7.0 mm. An external comparison, with respect to International Earth rotation and Reference systems Service (IERS) 08 C04 results, shows that standard deviations of polar motion $X_P$ and $Y_P$ are 0.754 milliarcseconds (mas) and 0.576 mas, respectively. Our results of precise orbital and geodetic parameter estimation are reasonable and help advance research at ILRS AAC.

• 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.

• Proceedings of the Korean Society of Surveying, Geodesy, Photogrammetry, and Cartography Conference
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• 2007.04a
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• pp.43-46
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• 2007

This paper focuses on examining and evaluating recent results of the national wide horizontal network adjustment which has carried out with respect to the Korean Geodetic Datum 2002 (KGD2002). To do this, 137 geodetic control points were observed by modem GPS technology. After processing all the observations, their outcomes are compared with ones provided by the national wide network adjustment. Results of GPS network show that RMSE is ${\pm}2.7cm\;and\;{\pm}6.5cm$ in horizontal and vertical component, respectively. On the other hand, ones from comparison with EDM network indicate that RMSE is ${\pm}3.0cm$ in horizontal component.