• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.7 no.2
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• pp.1-6
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• 1989

The adjustment of levelling net is being done to the order of nets independently by using the least square method. For the small size net, it has difficulties in verification and statistical analysis of the net since the degree of freedom is low At the same time, it is also difficult to evaluate the error of lower order net correctly. The aim of this study is to analyse the properties of combined adjustment method compared with the independent adjustment method by using the data which have been measured during 1967-1987. Another aim is to analyse the influences of normal orthometric correction and changes of datum. Finally, Korean leveling net has been evaluated by applying real redundancy and variance component estimation.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.28 no.2
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• pp.217-222
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• 2010

The geoid is the level surface that closely approximates mean sea level and usually used for the origin of vertical datum. For the computation of geoid, various sources of gravity measurements are used in South Korea and, as a consequence, the geoid models may show different results. however, a limited analysis has been performed due to a lack of controlled data, namely the GPS/Leveling data. Therefore, in this study, the gravimetric geoids are compared with the geodetic geoid which is obtained through the GPS/Leveling procedures. The gravimetric geoids are categorized into geoid from airborne gravimetry, geoid from the terrestrial gravimetry, NGII geoid(geoids published by National Geographic Information Institute) and NORI geoid(geoi published by National Oceanographic Research Institute), respectively. For the analysis, the geometric geoid is obtained at each unified national control point and the difference between geodetic and gravimetric geoid is computed. Also, the geoid height data is gridded on a regular $10{\times}10-km$ grid so that the FFT method can be applied to analyze the geoid height differences in frequency domain. The results show that no significant differences in standard deviation are observed when the geoids from the airborne and terrestrial gravimetry are compared with the geomertric geoid while relatively large difference are shown when NGII geoid and NORI geoid are compared with geometric geoid. Also, NGII geoid and NORI geoid are analyzed in frequency domain and the deviations occurs in long-wavelength domain.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.22 no.1
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• pp.29-36
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• 2004

This study describes the development of coordinate transformation tool for transforming the digital map using newly derived transformation parameters which are determined from the data referred to the local geodetic datum and the geocentric datum (ITRF2000) and the distortion modelling derived from collocation method. We prepared 190 common points and used 107 points to calculate 7 transformation parameters. In order to evaluate an accuracy of coordinate transformation, 83 common points were tested. In this study, we used Molodensky-Badekas model to derive the 7 transformation Parameters. An accuracy of 0.22m was obtained applying 7 Parameters transformation and the distortion modelling together. It shows that the accuracy of coordinate transformation is improved 72% against the result of 7 parameters transformation only. We developed the transformation tool, GDKtrans, which can be transformed the digital map of scales 1/50,000, 1/25,000 and 1/5,000. We also analyzed the digital map of l/5,000 at six urban areas by GPS observations. The result shows less RMSE of about 1.9 m and large disagreement at position and features. Consequently, we suggests that l/5,000 digital map is necessary of whole revision.

• Journal of Positioning, Navigation, and Timing
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• v.6 no.4
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• pp.211-221
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• 2017

Ellipsodially referenced survey (ERS) is considered as one of the challenging issues in the hydrographic surveys due to the fact that the bathymetric data collected by this technique can be readily transformed either to the geodetic or the chart datum by application of some geoscientific models. Global Navigation Satellite Systems (GNSS) is a preferred technique to determine the ellipsoidal height of a vessel reference point (RP) because it provides cost-effective and unprecedentedly accurate positioning solutions. Especially, the GNSS-derived heights include heave and dynamic draft of a vessel, so as for the reduced bathymetric solutions to be potentially free from these corrections. Although over the last few decades, differential GNSS (DGNSS) has been widely adopted in the bathymetric surveys, it only provides limited accuracy of the vertical component. This technical barrier can be effectively overcome by adopting the so-called GNSS carrier phase (CPH) based techniques, enhancing accuracy of the height solution up to few centimeters. From the positioning algorithm standpoint, the CPH-based techniques are categorized under absolute and relative positioning in post-processing mode; the former is precise point positioning (PPP) correcting errors by the global or regional models, the latter is post-processed kinematic positioning (PPK) that uses the differencing technique to common error sources between two receivers. This study has focused on assessment of achievable accuracy of the ellipsoidal heights obtained from these CPH-based techniques with a view to their applications to hydrographic surveys where project area is, especially, few tens to hundreds kilometers away from the shore. Some field trials have been designed and performed so as to collect GNSS observables on static and kinematic mode. In this paper, details of these tests and processed results are presented and discussed.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.1D
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• pp.167-173
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• 2011

This paper analyzes the procedure of calculating how the results of national control points (triangulation points), based on Bessel datum, have been transformed into those of KGD2002, based on the world geodetic system. GPS and EDM data observed from 1974 to 2008 were used for this purpose. A large-scale integrated GPS network was constructed to estimate the results of KGD2002 and new national control points about 12,000 were decided through multiple stages of data processing. The accuracy of these results is ${\pm}0.015m$ (95%) in the horizontal direction and ${\pm}0.030m$ (95%) in the vertical direction. The adjusted results verified by the construction of an integrated GPS/EDM network were compared with the results of KGD2002. In conclusion, the bulletin results are thought to be appropriate because the coordinate differences (RMSE) are ${\pm}0.0025m$ and ${\pm}0.008m$ in horizontal and vertical directions respectively.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.19 no.4
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• pp.415-423
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• 2001

This paper deals with the data processing method relative to reference frames through the calculation of absolute coordinates of permanent GPS site which was established at Sungkyunkwan University. In this paper. we computed the ITRF97 coordinates with high precision (0.0001 ppm) from GPS data analysis. Also, we derived the accurate coordinates referred to WGS84 and Korean Geodetic Datum (KGD) using transformation parameters provided. ITRF97 coordinates were computed by using the GIPSY-OASIS II (GOA II) software and the algorithms for determining the position developed Jet Propulsion Laboratory (JPL). The coordinates referred to WGS84 and KGD were derived from the transformation parameters provided by International Earth Rotation Service (IERS) and National Geography Institute (NGI). The parameters determined by NGI were calculated from the 2000 project of the establishment of geocentric coordinate system. We tested its availability through the comparison of the coordinates obtained from local GPS data analysis.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.30 no.3
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• pp.249-258
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• 2012

In this study, the epoch adjustment model was developed to correct GPS precise point positioning result to be suitable for the current geodetic datum of Korea which is tied at past epoch statically. The model is based on the formula describing crustal movements, and the formula is composed of several parameters. To determine the parameters, the data gathered at 14 permanent GPS stations for 10 years, from 2000 to 2011, were processed using GIPSY-OASIS II. It was possible to determine the position of permanent GPS stations with an error range of 16mm and the position of check points with an error range of 12mm by appling the model to GPS precise point positioning result. It is considered that more precise model could be calculated by using GPS data of more permanent GPS stations.

• Journal of the Economic Geographical Society of Korea
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• v.10 no.2
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• pp.167-181
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• 2007

The newly adopted Korea Geodetic Datum (a.k.a. KGD2002) calls for massive reengineering work on geospatial dataset. The main focus of our study is placed on the strategy and system implementations of the required data reengineering with a keen attention to integrated approaches to interoperability, standardization, and database utilization. Our reengineering strategy includes file-to-file, file-to-DB, DB-to-file, and DB-to-DB conversion for the coordinate transformation of KGD2002. In addition to the map formats of existing standards such as DXF and Shapefile, the newly recommended standards such as GML and SVG are also accommodated in our reengineering environment. These four types of standard format may be imported into and exported from spatial database via KGD2002 transformation component. The DB-to-DB conversion, in particular, includes not only intra-database conversion but also inter-database conversion between SDE/Oracle and Oracle Spatial. All these implementations were carried out in multiple computing environments: desktop and the Web. The feasibility test of our system shows that the coordinate differences between Bessel and GRS80 ellipsoid agree with the criteria presented in the existing researches.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.24 no.2
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• pp.193-200
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• 2006

Geographic information and surveying products are a momentous national infrastructure since it is an essential basis for land management and environmental preservation. Hence, it is necessary to set up a systematic plan and countermeasure for the upcoming unification of Korea. Otherwise there would be tremendous confusion and it will cause enormous expenses to establish the national surveying and geographical information standard. In order to show the vision of policies preparing for the unification of North and South Korea, we analyzed the case of Germany and the current status of surveying and Geographical Information in South and North Korea by taking the internet investigation, having a seminar, interviewing experts, and visiting related organizations. First of all, we should predict the change of surveying circumstances after the reunification and establish a plan that unifies laws, systems, and surveying standards of North and South Korea. We need to modify the datum point and unify the surveying product of South and North Korea in World Geodetic System. To accomplish these goals, we must make the map of Korean peninsula and neighboring nations, especially urban area of North Korea. It is considered that National Geographic Information Institute should take a major role in the unification of Korea. With these active preparations and plans, we will achieve the goals of establishing the reinforced surveying policy and minimizing the reunification expenses.