• Proceedings of the Korean Association of Geographic Inforamtion Studies Conference
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• 2008.10a
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• pp.203-204
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• 2008

EGM96 지구중력장모델을 개선시킨 EGM2008 지구중력장모델이 미국 NGA에 의해 발표됨에 따라, 본 연구에서는 EGM2008지구중력장모델을 한반도 지역을 대상으로 최대차수 360으로 해석하여 기존의 지구중력장모델인 EGM96(360차수) 및 EIGEN-GL04C(360차수)와 비교하였다. 또한 EGM2008은 기존의 구면조화분석한계인 360차수를 뛰어넘고 있으므로 격자 간격 $30'{\times}30'$ 및 $15'{\times}15'$, 그리고 $10'{\times}10'$로 각각 해석하여 지오이드고를 계산하고 정확도를 평가하였다. 정확도 평가는 우리나라의 수준점에서 GPS측량을 실시한 464점의 GPS/leveling 데이터를 활용하였다. 평가결과 EGM2008(360차수)은 $-0.100{\pm}0.183m$를 나타내 EGM96(360차수)결과인 $0.156{\pm}0.238m$에 비해 상당한 정확도의 개선을 가져왔으며, 2190차수의 고차항으로 해석한 결과 $-0.069{\pm}0.140m$ 더욱 정확한 결과를 얻을 수 있음을 확인하였다.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.1D
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• pp.161-166
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• 2009

High-resolution, high-precision ultra-high degree earth gravitational model are significant for the development of geodesy, geophysics, geodynamics and oceanography. In this research, we introduces the ultra-high earth gravitational model EGM2008 recently announced by U.S. NGA, reviews the issues and status of the ultra-high degree gravitational model development, and analyzes the accuracy of the gravitational model in Korea. First, EGM2008 is compared with the gravitational model EGM96 and Korea high-precision hybrid geoid model KGEOID08. In addition, the absolute accuracy is evaluated by ellipsoid height and orthometric height of a satellite geodetic reference point. Overall, the results show a similar accuracy between EGM2008 and KGEOID08. Thus, EGM2008 will be helpful for the future development of regional geoid and analysis of global gravity field.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.15 no.9
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• pp.1833-1839
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• 2011

In this study, Global Gravitational Model EGM2008, EGM96 and 16,786 gravity points measured on land were compared and analyzed. On the assumption that land gravity data is most accurate, the correlation coefficient, differences, MSE and difference variance along the height were computed between land gravity data and EGM2008, EG96. The correlation coefficient, land gravity data and EGM2008, was computed most largely with 0.824 and the correlation coefficient with EGM96 was computed with 0.538. The standard deviation of differences between land gravity and EGM2008, EGM96 were 13.196 magl, 18.685 mgal respectively. Also the difference variance scope of EGM2008 was smaller than EGM96. There was no large variance of free-air anomaly differences between land gravity data and EGM2008 along the height however free-air anomaly differences with EGM96 varied along the height changes. Consequently EGM2008 nicely expresses Korea gravity field more than EGM96.

• Journal of Korean Society for Geospatial Information Science
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• v.16 no.3
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• pp.117-126
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• 2008

Earth geopotential models were used to determine the reference surface in geoid modelling and many global geopotential models were developed after 1980's. Nowadays, EGM96 and EIGEN-GL04C geopotential models have been most widely used in the world, but what so called EGM2008 earth geopotential model were developed in 2008 by NGA. In this paper, we intended to compare the results of spherical harmonic analyses using the three geopotential model, EGM96, EIGEN-GL04C and EGM2008. So, the spherical harmonic analyses were performed up to degree and order 360(in case of EGM2008, up to degree and order 720, 1440, 2190 in addition), on each $1'{\times}1'$grid point in and around Korean peninsula. Geometric geoid were calculated at 464 GPS/leveling points for accuracy evaluation and then the results of three geopotential models were compared to geometric geoid. The results show that the accuracy of EGM2008 is improved considerablely compared to EGM96 and EIGEN-GL04C and it is possible to calculate geoidal heights within 14cm standard deviation and 5.5cm standard deviation after LSC fitting in and around Korean peninsula using EGM2008 geopotential model.

• The Journal of the Korea Contents Association
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• v.8 no.9
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• pp.274-280
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• 2008

The new high order Earth's gravity Model(EGM2008) are expected to improve the application about the Earth's global gravity field. The objectives of this research are to present characteristics on the geoid heights of provinces in South KOREA which calculated from the height anomalies by Earth Gravity Models. For this, seven EGMs (EGM2008<2,190>, EGM2008<360>, EGM96, EIGEN-GL04C, EIGEN-CG03C, EIGEN-GL04S1, and ITG-Grace02S) selected. Geoid heights of fifty BM check points by GPS/levelling are compared with those by NORI-05 model and seven EGMs. And also, geoid heights of 30"$\times$30" grid points in land(sixes blocks ; $1^{\circ}\times1^{\circ}$ sampled) and sea (four blocks ; $1^{\circ}\times1^{\circ}$ sampled) areas of South KOREA by EGM2008 are compared with those by NORI-05 and six EGMs. The results show that geoid heights obtained from EGM2008(2,190) of NGA displayed the nearest results to those by GPS/levelling.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.22 no.1
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• pp.45-52
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• 2004

It can be classified in various methods to get the geoidal heights. It can be achieved geometric geoidal heights if we do GPS surveying in leveling point. The aims of this paper are calculation of geometric geoidal heights using GPS/leveling data in study area and evaluation of the global and local geoid models in and around Korean peninsula. For this study, study area was selected in the leveling line from Kunsan to Chonju city and GPS surveying was accomplished in the leveling line. And, also spherical harmonic analysis was made on the three global geopotential models, OSU91A, EGM96, EGM96m under same condition. Then the differences were calculated between geometric geoidal heights and geoidal heights of 3 geopotential models, KOGD2002 which was Korean gravimetric geoid model. The results shows that EGM96m is the best model because the differences between geoidal heights of E6M96m and geometric geoidal heights of GPS/Leveling data appear the smallest value among them.

• Proceedings of the Korea Contents Association Conference
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• 2007.11a
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• pp.942-946
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• 2007

The new gravity field combination models are expected to improve the knowledge of the Earth's global gravity field. This study evaluates six global gravity field models derived from gravimetry and altimetry surface data in a comparison with ground truth in South Korea. For calculating a more accurate estimate of the geoid heights from the height anomalies, the terrain corrections due to the terrain masses over geoid have considered, the model for the topographic correction is a spherical harmonic expansion of the ETOPO2 DTM model. Geoid heights obtained from GPS and levelling in land area of South Korea are compared with those from the EGMs. The results show that EIGEN-CG03C EGM and EIGEN-GL04C EGM displayed the nearest results to GPS/leveling, and also confirmed the importance of terrain correction for geoid height in case of the uneven topography.

• Korean Journal of Remote Sensing
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• v.22 no.4
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• pp.255-264
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• 2006

GRACE (Gravity Recovery and Climate Experiment) is the first dedicated gravity mapping mission. Its primary measurements are the distance changes between two co-orbiting low earth satellites. GRACE is a joint development by NASA and German DLR and was launched in March 2002. GRACE improves the Earth gravity model accuracy by nearly two factor of magnitude over pre-launch models. After brief description of the GRACE primary instrument, inter-satellite ranging system, its flight status and preliminary performance evaluation is presented. Ranging system error models, which were not included in the pre-launch performance model and design specifications, are identified through analyzing the flight data. Base on this analysis, future research topics on the GRACE instrument performance analysis are discussed.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.23 no.4
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• pp.353-358
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• 2005

The purpose of this paper is to evaluate a new geopotential model, EIGEN-CG01C which had been developed from CHAMP and GRACE mission observations and surface gravity data. The accuracy analysis was conducted by comparing the geoidal heights computed from two types of geopotential models (i.e., EIGEN-CG01C and EGM96) with spirit leveled GPS bench mark. To this end, three hundred twenty GPS leveled bench marks are used as bases for the numerical investigation. From the analysis, it was possible to conclude that EIGEN-CG01C was more suitable to upgrade the KGEOID 98 since the results that the EGM96 was slightly biased.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.31 no.3
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• pp.239-247
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• 2013

The global gravitational model is essential for precision geoid model construction. Also, it would be used as basic scientific data in geophysical and oceanographic fields. In Korea, EGM2008 has been used from the late 2000s. After publishing EGM2008, new gravitational models such as GOCO02S, GOCO03S, EIGEN-6C, EIGEN-6C2 based on GOCE data were developed. Therefore, we need to verify recent models to select optimal one for geoid computation in Korea. In this study, we compared new models generated based on the GOCE data to EGM2008 and verified the precision of models by comparing with NGII(National Geographic Information Institute) GPS/Leveling data. When comparing EIGEN models to EGM2008, the difference is about 8cm. On the other h and, about 70cm of difference between GOCO models and EGM2008 has been calculated. The reason for this is because GOCO models have been developed using only satellite data while EGM2008 has been used gravity and altimeter data as well as satellite data. When comparing global gravitational model to GPS/Leveling data, EGM2008 showed the best precision of 6.1cm over whole Korean peninsula. The new global gravitational model using additional GOCE data will be published consistently, so the precision verification of new model should be continued.