• 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 Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.13 no.2
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• pp.237-244
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• 1995

In this study, we made WGS84 geoidal height model from GPS measurements for bench marks and calculated geoidal height of B.Ms which were selected check points using the hi-linear, trend surface fitting and triangulation interpolation method. From these, the interpolation accuracy was studied. Also, we tried to study accuracy of height transformation by making up orthometric height with latitude and longitude on Bessel ellipsoid for bench marks which were calculated by applying transformation parameters that were got GPS measurements for precise primary control stations. As a result of this study, the WGS84 geoidal height and orthometric height could be determined as a deviation value of 20 cm.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.13 no.5
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• pp.183-190
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• 1993

Determining accurate geoid height is very important because it is the basis of the 3-D coordinate transformation and determination of the orthometric height. In this study, for determining the geoid height, bi-linear method grounded on the interpolation method, GPS leveling and OSU91A was applied to the $5km{\times}5km$ area and $60km{\times}60km$ area in the latitude $N\;36^{\circ}{\sim}37^{\circ}$ and the longitude $E\;127^{\circ}{\sim}128^{\circ}$. The results obtained by these methods were compared with conventional leveling data. In case of bi-linear method, it was dependent upon the shape of interpolation network and undulation of ground. If leveling data are satisfactory, GPS leveling is more proper than any other method. Also, it is 62 cm that an average difference of GPS leveling and OSU91A. As a result, in order to determine more precise geoid height, the development of local geoid model is a pressing problem to be solved. The result of the research will provide reference data for settling the 3-D coordinate transformation, and it is expected that it will also be applied to determination of 3-D position.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.16 no.2
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• pp.213-223
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• 1998

This paper deals with the geoid modelling in and around Korean peninsula referred to Bessel ellipsoid. Several useful data were used to compute precise geoidal heights referred to GRS80 by remove and restore technique and FFT technique was used to evaluate Stokes' integral. All grid point elevations extracted from GTOPO 30 and Bessel coordinates of all grid point were computed through coordinates transformation by applying three transformation parameters. Finally, geoidal heights referred to Bessel ellipsoid were calculated by geometric method. As the results of this study, a precise gravimetric geoid model referred to GRS80 (KOGGDM33) and geoid model referred to Bessel ellipsoid(KOBGDM33) in and around Korean peninsula were developed. KOBGDM33 shows the gradual distribution of geoidal heights from -91.8 m in Yongampo to -39.0 m in the straits of Korea.

• Journal of Korean Society for Geospatial Information Science
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• v.2 no.2 s.4
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• pp.143-151
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• 1994

3-D coordinates that result form GPS survey are not applied directly in korea because they are based on WGS 84 ellipsoid. Thus they must be transformed into longitude, latitude on the Bessel ellipsoid and orthometric height. Transformation parameters must be determined in order to perform the coordinate transformation. Also, coordinate transformation be preformed on longitude, latitude and ellipsoidal height. First estimation of Bessel geoidal height must be accomplished to acquire Bessel ellipsoidal height This paper suggests accuracy of coordinate transformation according to the estimation method of Bessel geoidal height. Also, This paper suggests that Bessel geoidal height have influence on the coordinates transformation.

• Journal of Korean Society for Geospatial Information Science
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• v.15 no.1 s.39
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• pp.47-53
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• 2007

Astronomic surveying has been regarded as an important method for absolute positioning of geodetic datum in each countries under the local geodetic reference system. The purposes of this study are to determine astrogeodetic geoidal heights referred to Bessel ellipsoid and to determine deflection of the vertical and geoidal heights referred to GRS80 of World Geodetic System by astronomic surveying data which have been surveyed after 1970 in Korea. The results show that $\xi$ component of the deflection of the vertical distribute from -5.725" to 8.005" and $\eta$ component distribute from -14.917" to 6.2" and astrogeodrtic geoidal heights distribute from 23 m to 27 m in the study area. Also, we could see that GRS80 was more optimal ellipsoid than Bessel 1841 ellipsoid to Korea through comparing both astrogeotic geoidal heights referred to GRS80 and Bessel 1841 ellipsoid.

• Journal of the Korean Society for Railway
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• v.12 no.4
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• pp.499-505
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• 2009

This paper evaluated applicability of railroad reference points for determinating geoid heights. For this research, reference points on the Honam express raildroad which contain ellipsoid heights estimated by GPS/Leveling and orthometric heights by leveling were used. Geoid heights were calculated uisng orthometric and ellipsoid heights of 360 railroad reference points, and the RMSE's with respect to different intervals of reference points were analysed which were induced by interpolation methods. The results showed that no significant difference of RMSE's among interpolation. methods. RMSE's of 0-4km interval of reference points were determined within 2cm and 5-8km were within 3cm. Also, this research confirmed that GPS leveling with Geoid model is not auurate enough to be used for railroad surveying as yet.

• 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.

• 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.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.13 no.2
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• pp.125-133
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• 1995

The geoidal heights of a country may be computed from astrogedetic, gravimetric or satellite data. In this paper, the geoid models to the Bessel ellipsoid(KGM95-A) have been determined by the astrogedetic method, which is surface fitting techniques using deflections of the vertical and geoid height constraints. Transformation equations and the gravimetric geocentric geoid(KGM93-C) were applied to obtain the geoid height referred to the Tokyo Datum of the Korean geodetic network, the comparison of the astrogedetic results and discussions of the geoid information were added.