• 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.

• 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.

• 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.

• Proceedings of the Korean Association of Geographic Inforamtion Studies Conference
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• 2010.09a
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• pp.369-371
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• 2010

본 연구는 국내 중력 자료의 통합을 위한 정밀도 분석을 위해 지난 2008년부터 현재까지 진행 중인 통합기준점 사업으로 인해 측정된 중력 자료를 기반으로 국내 중력 자료의 정밀도를 분석하였다. 연구에 사용된 중력 자료는 전국에 설치된 통합기준점 805점과 수준점 1424점이 이용되었으며, 이는 일정한 처리 과정을 거쳐 정밀도 분석이 수행되었다. 분석된 자료는 부분적으로 약간의 편차를 가졌으며 각 기기별, 노선별, 일정에 따른 대동소이한 차이를 나타내었다. 본 연구의 자료 처리 과정에 있어 국내 중력 자료의 다양한 문제점과 처리 과정에서의 어려움을 발견하고 이러한 문제점을 분석하였다.

• 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.

• Proceedings of the Korean Association of Geographic Inforamtion Studies Conference
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• 2010.06a
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• pp.281-282
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• 2010

우리나라의 수직기준은 인천만의 평균해수면으로 이 높이를 기준으로 수준점의 표고를 결정한다. 현재 우리나라 수준점의 고시성과는 실제 중력의 영향을 고려하는 대신 정규중력식에 의한 타원보정량을 계산하여, 높이차를 보정한 뒤 수준원점을 고정하고 최소제곱법을 수행하여 산출한 정규표고이다. 하지만 우리나라의 경우 산지가 많아 지형의 기복이 심하고 산맥을 가로지르는 수준노선이 있어 중력에 의한 영향을 무시할 수 없으나 현재 그 영향을 고려하고 있지 못하고 있는 실정이다. 따라서 본 연구에서는 항공 중력데이터를 이용하여 수준점의 중력값을 산출한 뒤 정표고를 산출하여 현재 사용하고 있는 고시좌표와 비교해 보고자한다.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.29 no.1
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• pp.81-89
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• 2011

The previous land gravity data in Korea showed locally biased irregular distribution. Especially, this problem was more serious in the mountainous area where the data density was significantly low. The same problem appeared in GPS/Levelling data thus the precision of the geoid could not be improved. From 2008, new gravity and GPS/Levelling data has been collected by the unified control point and survey on the benchmark project which were funded by the national geographic information institute. The newly obtained data has much better distribution and precision so that it could be used for update precision of geoid model. In this study, the new precision geoid has been calculated based old and new gravity data and this model showed 5.29cm of precision compared to 927 points of GPS/Levelling data. And the degree of fit and precision of hybrid geoid has been calculated 2.99cm and 3.67cm. The new gravimetric geoid has been updated about 27% over whole country. And it showed 42% of precision update due to collection of new gravity data on the Kangwon/Kyeongsang area which showed quite low distribution. In 2010, about 4,000 points of gravity and 300 points of GPS/Levelling data has been obtained by unified control and survey on benchmark project. We expect that new data will contribute to updating geoid precision and veri tying precision more objectively.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.28 no.1
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• pp.99-106
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• 2010

A vertical datum requires an origin, which is a point on the Earth's surface where the height of the point is a defined value(26.6871m). From this origin point, heights (height differences) can be measured to any other point using standard leveling and gravity measurement procedures. However, the leveling network over the Korea bas been established by using the normal gravity instead of the actual gravity values, and the heights for the points are published by National Geographic Information Institute (NGII). This may cause height for especially in the area where high-relief mountains are dominant. Therefore, the height errors caused by using normal gravity instead of actual gravity values are analyzed in this study. Then, the differences between the orthometric heights and the published heights, i.e., normal orthometric height are analyzed.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.30 no.5
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• pp.493-500
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• 2012

The previous geoid model developed in early 2000s shows 14cm level of precision due to the problems on distribution, and quality of the land gravity and GPS/Leveling data. From 2007, the new land and airborne gravity data as well as GPS/Leveling data having high quality and regular distribution has been obtained. In 2011, a new gravimetric geoid model has been constructed with precision of 5.29cm which was improved about 27% comparing to the previous model. However, much more land gravity data has been collected at the control point, bench marks and triangulation points since 2010. Also, GPS/Leveling data having 10km spacing over whole country has been obtained through the project which is for the construction of new control points. In this study, new gravimetric geoid has been calculated based on the all available gravity data up to present. The geoid height shows the range from 18.05m to 32.70m over whole country and its precision is 5.76cm. The degree of fit and precision of hybrid geoid model are 3.60cm and 4.06cm, respectively. At the end, 3.35cm of the relative precision in 15km baseline has been calculated to confirm its practical usage. Especially, it has been founded that regional bias occurred at the Kangwon and coastal area due to problems on the leveling data. Also, some inland points show inconsistent large difference which needs to be verified by analyzing the unified control points results.

• 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.