• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.2D
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• pp.323-334
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• 2011

In this study, we performed the residual geoid modeling using the FFT and LSC methods in context of application of R-R (Remove and Restore) technique as a general technique for gravimetric geoid model in order to propose the effective way of geoid determination in Korea. For this, a number of data compiled for residual geoid modeling by the multi-band spherical FFT method with Stoke's formula and LSC method as known as statistical method. The geometric geoidal heights obtained from 503 GPS/Levelling data were used for inducing the various elements and proper computation process which should be considered for improving the accuracy of residual geoid modeling. Finally, we statistically compared the results of residual geoid heights between FFT and LSC methods and reviewed then the proper way of residual geoid modeling to the region of Korea. As the results of comparison, LSC method is not suitable for residual geoid modeling in Korea due to the noise and lack of gravity observations and the effects of local characteristics, while FFT method by applying Stokes' integral with proper cap size and modified kernel which provides the better accuracy of residual geoid heights up to 10 cm more than those of LSC method.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.7
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• pp.4595-4600
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• 2014

A geoid has great meaning as a vertical reference plane, and at this point when GPS measurement is vitalized, it is an important factor that makes level measurements with GPS possible. This study carried out GPS and leveling of newly created complex control points targeting Daejeon. The geoid for the precise area was built by calculating the plane location, elevation and the geoid of each reference point using GPS/Leveling. In addition, this study evaluated the potential of GPS leveling throughout the site calibration. The geoid for the precise area intervals of approximately 1.5km throughout the study was determined. The results highlight the possibility of leveling by estimating direct leveling performance and mean altitude deviation by less than 2cm. Based on the results, if a geoid model for the precise and wide area can be developed throughout ongoing research, survey tasks that require elevation can be streamlined and the efficiency maximized.

• Journal of Korean Society for Geospatial Information Science
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• v.25 no.2
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• pp.57-65
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• 2017

The purpose of this study is to analyze the feasibility of using Global Navigation Satellite System(GNSS)/Geoid technology in determining orthometric height in mountain. For the study, a test bed was set up in and around Mount Jiri and GNSS surveying were conducted. The orthometric height of 39 benchmarks was determined by applying the EGM2008, KNGeoid13, and KNGeoid14 geoid models and the accuracy was estimated by comparing with the offical Benchmarks orthometric height value issued by National Geographic Information Institute(NGII) and finally, the results were analyzed with the Aerial Photogrammetry Work Regulations. As a result of the study, it was found that the accuracy of the orthometric height determination by GNSS/Geoid technology was ${\pm}7.1cm$ when the KNGeoid14 geoid model was applied. And also, it can be confirmed that it is usable for the less than 1/1000 plotting scales as a vertical reference point for the aerial triangulation in Aerial Photogrammetry.

• Journal of Korean Society for Geospatial Information Science
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• v.10 no.2 s.20
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• pp.107-114
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• 2002

This study aimed to estimate accuracy of GPS/Leveling and to present availability of GPS/Leveling in public surveying. For this purpose, we carried out GPS survey for bench marks and control points of Hongsung area. Orthometric heights calculated by two GPS/Leveling methods were compared to reference height. The one is calculated by base of geoid models such as EGM96, OSU91A, KGEOID99, and the other is calculated by network adjustment using fixed point. The results of GPS/Leveling by geoid models show that RMSE of EGM96 is ${\pm}0.061m,\;OSU91A\;{\pm}0.725m,\;KGEOID99\;{\pm}0.598m$. The results of GPS/Leveling by network adjustment show that the best RMSE is ${\pm}0.043m$ in case of using three fixed bench mark, and this method can be used for leveling effectively. GPS/Leveling would be able to apply in forth order public leveling and height determination of public control points.

• 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.

• 한국해양학회지
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• v.29 no.4
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• pp.383-391
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• 1994

Sea surface height geoidal undulation, and gravity anomaly derived from satellite altimeter measurements are described. Assuming mean sea surface height (MSSH) as geoidal undulation, MSSH was converted to gravity anomaly. the result shows that the gravity anomaly derived from satellite altimeter data can be mapped to an accuracy of the surface ship gravity measurements. The data used for the conversion is the two-year mean sea surface height obtained from GEOSAT Exact Repeat Mission. The conversion was carried out using fast Fourier transform with plane approximation. In this process, the so called remove-restore method was employed.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.13 no.2
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• pp.291-298
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• 1995

This paper describes the test results of terrain corrections as the short wave length effect and geoid effects in gravity field modelling using Digital Terrain Model(DTM) in Korea. For a rigorous determination of terrain correction a dense grided DTM data wave prepard spacing $500\times{500m}$ was used for the computation of terrain effects. From the results obtained by the mass prism model and the mass line model, we were found that the terrain effects are large depend on the topography in the test area. It means that we should considered the terrain effects for the precise geoid determination.

• 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.34 no.1
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• pp.91-98
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• 2016

In order to apply Kriging methods for geostatistics of spatial data, an estimation of spatial coherency functions is required priorly based on the spatial distance between measurement points. In the study, the typical coherency functions, such as semi-variogram, homeogram, and covariance function, were estimated using the national geoid model. The test area consisting of 2°×2° and the Unified Control Points (UCPs) within the area were chosen as sampling measurements of the geoid. Based on the distance between the control points, a total of 100 sampling points were grouped into distinct pairs and assigned into a bin. Empirical values, which were calculated with each of the spatial coherency functions, resulted out as a wave model of a semi-variogram for the best quality of fit. Both of homeogram and covariance functions were better fitted into the exponential model. In the future, the methods of various Kriging and the functions of estimated spatial coherency need to be studied to verify the prediction accuracy and to calculate the Mean Squared Prediction Error (MSPE).

• KSCE Journal of Civil and Environmental Engineering Research
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• v.13 no.1
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• pp.141-149
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• 1993

The gravimetric geoid of the South Korea Region was computed on Geodetic Reference System 1980(GRS80) using a combination of satellite-derived potential coefficients and terrestrial gravaty data. $10^{\prime}{\times}10^{\prime}$ mean gravity anomalies were obtained from surface gravity data for the outer zones, $1^{\circ}{\times}1^{\circ}$ equal area mean anomalies were used for the inner zones, and point gravity anomalies were used for the innermost zones in the Stokes integration. The GRS80 potential coefficients were obtained from modification of GEM9 data and Integration was extended over a spherical cap of $30^{\circ}$ from the integration area. The results of a free-air geoid show that the systematic mean difference of approximately 2~3m in comparison of OSU89B model.