• Proceedings of the Korean Society of Surveying, Geodesy, Photogrammetry, and Cartography Conference
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• 2010.04a
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• pp.43-44
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• 2010

We present the analysis of space geodetic technique observation, Satellite Laser Ranging (SLR), to LAGEOS1 and LAGEOS2 for the definition of the Terrestrial Reference Frame (TRF). The data were analyzed in 7day arcs during about 9 years (2000/01/10 ~ 2008/12/29) using NASA Goddard's GEODYN/SOLVE II software. The comparison of the coordinates between ITRF2005 and TRF solutions determined in this work shows that there is no significant bias.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.29 no.4
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• pp.367-380
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• 2011

This paper has focused on deriving a GPS based geodetic network adjustment strategy to continuously determine coordinate sets of the national geodetic control points. After domestic literature review on the topic and overseas case studies about countries that recently reformed their geodetic infrastructure have been carried out, a simplified geodetic network consisting of two layers, namely GPS active and passive network, has been proposed to maximize effectiveness of the network adjustment through reducing the number of the passive points. Furthermore, a GPS data processing and network adjustment procedure has been derived to support the continuous management scheme. While a scheme for the active layer adopts a sequential least squares adjustment based on a multi-baseline, that of the passive layer employs a multi-session adjustment technique with respect to 3-dimensional baseline vectors. Finally, experimental adjustment against a network comprising 24 active and 6,900 passive stations has been performed to demonstrate the efficiency and the effectiveness of the proposed method.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.16 no.1
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• pp.85-94
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• 1998

In year 1996, the National Geography Institute(NGI) carried out a National Fundamental Network survey. A total of 220 baselines between 31 stations were occupied that the baseline length is 40 km-120 km(mean 67.4 km). A minimally constrained network adjustment with three dimensional baseline vectors, was carried out holding geocentric ITRF94 coordinates of the station SUWON which are determined by eccentric observations from the VLBI station. This paper shows KTRF94 coordinates of fundamental stations which accuracies are estimated 1 cm in horizontal and 3 cm in vertical. Also, the coordinates are compared to WGS84 and/or KGS95.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.25 no.5
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• pp.465-474
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• 2007

This paper focuses on examining and evaluating results of the Korean Geodetic Datum 2002 (KGD2002) of the national horizontal network adjustment. To this end, 137 geodetic control points were independently observed by GPS technology. After processing all the observations, their results were compared with ones derived by the national network adjustment which was recently performed to determine new KGD 2002 coordinate sets over the national geodetic control points. The comparisons results showed that RMSE was ${\pm}2.7cm$ and ${pm}6.5cm$ in horizontal and vertical component in the case of GPS network, whereas RMSE was ${\pm}3.0cm$, in horizontal component in the case of EDM network.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.40 no.4
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• pp.315-324
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• 2022

The conventional LESS (LEast-Squares Solution) is calculated under the assumption that there is no errors in independent variables. However, the coordinates of a point, either from traditional ground surveying such as slant distances, horizontal and/or vertical angles, or GNSS (Global Navigation Satellite System) positioning, cannot be determined independently (and the components are correlated each other). Therefore, the TLS (Total Least Squares) adjustment should be applied for all applications related to the coordinates. Many approaches were suggested in order to solve this problem, resulting in equivalent solutions except some restrictions. In this study, we calculated the normal vector of the 3D plane determined by the trace of the VLBI targets based on TLS within GHM (Gauss-Helmert Model). Another numerical test was conducted for the estimation of the Helmert transformation parameters. Since the errors in the horizontal components are very small compared to the radius of the circle, the final estimates are almost identical. However, the estimated variance components are significantly reduced as well as show a different characteristic depending on the target location. The Helmert transformation parameters are estimated more precisely compared to the conventional LESS case. Furthermore, the residuals can be predicted on both reference frames with much smaller magnitude (in absolute sense).

• Geophysics and Geophysical Exploration
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• v.18 no.3
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• pp.133-142
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• 2015

Displacement of the Earth's surface due to atmospheric loading has been recognized since a century years ago, and its accurate estimation is required in present day geodesy and surveying, particularly in space geodesy. Atmospheric load deformation in continental region can readily be calculated with the given atmospheric pressure field and the load Green's function, and, in near coastal area, approximate model is used for the calculation. The changes in the Earth's atmospheric circulation and the seasonal variation of atmospheric pressure on two hemispheres of the Earth are the each main causes of variation of the Earth's spin angular velocity and polar motion respectively. Wind and atmospheric pressure do the major role in other periodic and non-periodic perturbations of the positions in the Earth's reference frame and variations in the Earth's spin rotational state. In this reviewing study, the developments of related theories and models are summarized along with brief description of phenomena, and the geodetic perturbing effects of a hypothetical typhoon passing Korea are shown as an example. Finally related existing problems and further necessary studies are discussed in general.

• Ocean and Polar Research
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• v.23 no.2
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• pp.121-130
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• 2001

Geodetic datums define the size and shape of the earth and the origin and orientation of the coordinate systems used to map the earth. A lot of different datums have been developed and each nation uses its own datum as the basis for coordinate systems used to identify positions in geographic information systems. Recently GPS receivers are widely used to find out location and GPS is based on the World Geodetic System 1984(WGS-84) datum. Therefore the diversity of datums in use today requires accurate conversion between coordinates in different datums. In this study a coordinate conversion program on Windows is developed to transform between Tokyo Bessel(1941), which is the reference datum in Korea, and WGS-84. Several examples of coordinate conversion are presented and computed results are tested and proved to be correct.

• Proceedings of the Korean Information Science Society Conference
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• 2006.06b
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• pp.232-234
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• 2006

본 논문에서는 마르코프 결정 문제 (Markov decision problem)의 풀이 효율을 잴 수 있는 척도를 알아보기 위해 복잡계 네트워크 (complex network) 의 관점에서 MDP를 하나의 그래프로 나타내고, 그 그래프의 위상학적 성질들을 여러 네트워크 척도 (network measurements)들을 이용하여 측정하고 그 MDP의 풀이 효율과의 관계를 분석하였다. 실세계의 여러 문제들이 MDP로 표현될 수 있고, 모델이 알려진 경우에는 평가치 반복(value iteration)이나 모델이 알려지지 않은 경우에도 강화 학습(reinforcement learning) 알고리즘등을 사용하여 풀 수 있으나, 이들 알고리즘들은 시간 복잡도가 높아 크기가 큰 실세계 문제에 적용하기 쉽지 않다. 이 문제를 해결하기 위해 제안된 것이 MDP를 계층적으로 분할하거나, 여러 단계를 묶어서 수행하는 등의 시간적 추상화(temporal abstraction) 방법들이다. 시간적 추상화를 도입할 경우 MDP가 보다 효율적으로 풀리는 꼴로 바뀐다는 사실에 착안하여, MDP의 풀이 효율을 네트워크 척도를 이용하여 측정할 수 있는 여러 위상학적 성질들을 기반으로 분석하였다. 다양한 구조와 파라미터를 가진 MDP들을 사용해 네트워크 척도들과 MDP의 풀이 효율간의 관계를 분석해 본 결과, 네트워크 척도들 중 평균 측지 거리 (mean geodesic distance) 가 그 MDP의 풀이 효율을 결정하는 가장 중요한 기준이라는 사실을 알 수 있었다.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.1 no.2
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• pp.42-59
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• 1983

This article investigates the situation of the Plane Rectangular Coordinate derived from the Gauss Double Projection whereby the positioning of triangulation point in Korea has been represented on. Analyzing and assessing it have been performed by means of new computational method such as computer programing. On the basis of the results brought about, it is found that a new Plane Rectangular Coordinate as well as map projection and scale factor of geodetic length may be adapted to improve the distortion along the geodetic line on a certain zone of map projection in order to enhance the accuracy and the utility of the practical surveying works. The proposals for this study are as follows; (1) projection: Gauss-Kruger's projection (2) Coordinate system: Plane Rectangular coordinate with 8 origin system (3) Scale factor of geodetic length in origin; $m_0=0.9999$

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.27 no.3
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• pp.303-310
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• 2009

We processed seven years data of 142 IGS(International GNSS Service) stations were processed, which have been selected with an optimal network algorithm, to realize terrestrial reference system. To verify the result, a comparison with the ITRF2005 was given both in positions and velocities with transformation parameters estimation. The transformation parameters are within 4.3 mm in length, while the RMS(root mean square) difference of positions and velocities are 6.7 mm and 1.3 mm/yr in horizontal and 13.3 mm and 2.4 mm/yr in vertical, respectively, which represent good coincidences with ITRF2005. This research would help developing our own geodetic reference frame and may be applied for the global earth observations such as the global tectonics. A further improved TRF would be expected by applying various data processing strategies and with extension of data in number and observation period.