• Journal of the Korean Geophysical Society
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• v.4 no.2
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• pp.121-131
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• 2001

We have established 88 auxiliary gravity reference stations by using two gravitimeters at the observation offices of the Korean meteorological agency and measured the locations by using GPS. All gravity values have been calculated on the basis of the gravity reference point at Pusan National University, thus, they have been established to bge easily converted to new absolute gravity value later. The increased numbers of the gravity reference stations will minimize errors due to measurements, drift correction etc. and increase the accuracy of the gravity data. The result of this research will be used to verify the gravity data which calculated with the relative gravity meter and to inspect relative gravity meters.

• Geophysics and Geophysical Exploration
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• v.24 no.1
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• pp.1-5
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• 2021

The closed-form expressions of the vector gravity and gravity gradient tensor due to a circular disk are derived. The gravity potential due to a circular disk with a constant density is defined for a cylindrical system. Then, the vector gravity is derived by differentiating the gravity potential with respect to cylindrical coordinates. The radial component of the vector gravity in the cylindrical system is converted into horizontal gravity components in the Cartesian system. Finally, the gravity gradient tensor due to a circular disk is obtained by differentiating the vector gravity with respect to the Cartesian coordinates.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.29 no.5
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• pp.543-550
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• 2011

The gravity anomaly is a basic geophysical data applied in various fields such as geophysics, geodesy and national defense. In general, the gravity anomaly is used through a interpolation process based on the constructed database. The gravity variation, however, is appeared in various shapes depending on the topography and the density of the underground structures. Therefore, the interpolation could lead to a large differences if the gravity fields do not satisfy the assumptions on the signal behavior like linear or a certain degree polynomials. Furthermore, the interpolation does not reflect the physical characteristics of the gravity such as the harmonic condition. In this study, the gravity modeling using the plane Fourier series and radial basis functions are performed to overcome the problems in the usual interpolation. The results of the modeling is analyzed for the case of the gravity referenced navigation focused on the signal characteristics. Based on the study, it was found that the results from modeling are not much different to that from the interpolation in a smoothly varied area. In case of the highly varied area, however, a large differences are appeared among the three methods. Especially, the Fourier series shows the most smooth variations in the modeled gravity values while the highest variations appeared in the interpolation. Applying to the gravity referenced navigation, it was found that the modeling is more effective in calculation cost. It is considered that the results from this study provides a basis on effective modeling of the gravity fields in terms of the signal characteristics and resolution for various application fields.

• Proceedings of the Korean Society of Surveying, Geodesy, Photogrammetry, and Cartography Conference
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• 2009.04a
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• pp.49-53
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• 2009

In this study, point gravity was measured to achieve terrestrid gravity data and the gravity is important element in precise geoid modelling. Surveys the relative gravity of 56 stations on 1st level route. In addition, it calculates gravity values, analysis gravity survey results using tidal correction, drift correction, datum-free adjustment. These point gravity data could be contribute in development of precise geoid model.

• Proceedings of the KSEEG Conference
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• 1999.04a
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• pp.127-129
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• 1999

현재 국내에서 사용되고 있는 중력 기준점은 서로 다른 2 개의 루트를 통하여 유도되었다. 따라서 중력에 관련된 업무를 수행하는 연구자에게는 서로간의 신뢰도 문제를 야기시키고 있다. 그러므로 본 연구의 목적은 이들의 중력 기준점의 값을 상호 비교 검토하여 올바른 중력 기준점 값을 제시하는 데 두고있다. 따라서 중력 기준점 값을 상호 비교검토을 위하여, 1973년도 한$\cdot$영, 1974년도 한$\cdot$일 협력에 의해서 이루어진 중력 기준점 : 구 국립지질광물연구소(서울), 국립지리원(구 서울시 동대문구 휘경동 소재) 및 표준연구소(대전)을 관측하였다. 그 결과, 절대 중력관측에 의한 중력 값이 결정되기까지는 국립지리원에서 국내에 설치한 중력기준점 값을 사용하는 것이 바람직하다.

• Economic and Environmental Geology
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• v.36 no.5
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• pp.387-389
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• 2003

For the establishing gravity base station and the improving the precision of exiting gravity network, and getting the gravity acceleration value in Korea, the absolute gravity measurements have been conducted at Daejeon(KRISS) from October 8 to November 8, 1996 with the NIM-II Absolute gravimeter and Suwon(NGI) from December 10 to December 16, 1999 with the FG5 Absolute gravity meter. The each absolute gravity value measured at KRISS and at NGI is 979,829.609${\pm}$0.006 mGal from 353 dropes and 979,918.775${\pm}$0.0001 mGal from a total 14,346 dropes. I think that we need the many base Absolute gravity station for the activation of the Earth science.

• The Korean Journal of Zoology
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• v.35 no.4
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• pp.518-525
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• 1992

본 연구에서는 horizontal clinostat과 원심분리 방법의 이용으로 각각 저중력 상태($\mu$G)와 고중력 상태(3G)를 유도하여, 중력장의 변화가 양서류 수정란의 초기 형태 형성에 미치는 영향을 북방산개구리(Rano dybows비름를 대상으로 조사하였다. 중력장의 변화는 첫번째 수평 분열인 제3분열면의 위치에 영향을 미쳤다. 즉 저중력 상태에서는 분열면이 적도면 근처에서, 또 고중력 상태에서는 분열면이 동물극 근처에서 형성되었다. 이와 같은 변화는 포배기로 이어져 할강의 위치와 동물극 정단 세포층 수에 영향을 미쳤다. 즉 저중력에 노출된 포배는 정상배(1G)에 비해 할강이 중앙에 위치했으며 동물극 정단의 세포층 수가 증가하는 반면 고중력에 노출된 포배는 할강이 보다 동물극 폭에 위치했으며 동물극 정단의 세포층 수도 감소하였다. 그러나 낭배기에 도달하면 동물극 정단 세포층 수의 차이는 정상 상태로 조절되었다. 한편 중력장의 변화는 낭배기에 이르는 발생 속도와 원구상순부의 위치를 변경시켰다. 낭배기 이후의 발생 단계에서 중력에 의한 변화로는 tail fin circulation(stage 22)시기의 머리크기의 변화를 들 수 있다. 이상의 결과로 무미 양서류의 초기 형태 형성은 중력장에 의해 변형될 수 있으며 이러한 변화는 발생이 진행됨에 따라 조절되는 것으로 보인다.

• Geophysics and Geophysical Exploration
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• v.25 no.1
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• pp.44-49
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• 2022

Closed-form expressions of vector gravity and gravity gradient tensor based on a line segment are derived. If a cylindrical object with axial symmetry is observed from a distance, it is possible to approximate it as a line segment; therefore, it is necessary to compute the gravity and the gravity gradient tensor due to a line source by using closed-form expressions. The gravitational potential for a line segment is defined as a one-dimensional integral, and this integral is differentiated with respect to the Cartesian coordinate system to derive the vector gravity. The expressions of the gravity gradient tensor are derived by differentiating the vector gravity once more in the same coordinate system.

• 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.

• Geophysics and Geophysical Exploration
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• v.9 no.2
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• pp.171-175
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• 2006

Gravity reduction and Bouguer anomaly are frequently misunderstood by many geoscientists as follows; the observed gravity is reduced to a common datum plane, so that gravity effects by all materials above the datum is removed, therefore, Bouguer anomaly is located on the datum plane. In reality, Bouguer anomaly does not lie on a common datum plane, but is difference between observed gravity and reference gravity at the actual point of measurement. Commonly used gravity reduction formulas are approximate formulas. Here, we introduce complete formulas, and suggest to use them for more accurate results. We also suggest to use not the geoid but the reference ellipsoid as the vertical datum.