• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.13 no.2
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• pp.177-185
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• 1995

Gravity anomalies were recovered on a $5'\times{5'}$grid using the sea surface height data obtained from the combination of Geosat, ERS-1, Topex/Poseidon altimeter data around Korean Peninsula bounded by latitude between $30^\circ{N}\;and\;50^\circ{N}$ and longitude $120^\circ{E}\;to\;140^\circ{E.}$ In order to recover the gravity anomalies from SSH(Sea Surface Height), inverse FFT technique was applied. The estimated gravity anomalies were compared with gravity anomalies measured by shipboard around Korean Peninsula. In comparison with the differences of gravity anomaly between measured data and altimeter data, the mean and the standard deviation were found to be -0.51 mGal and 13.48 mGal, respectively. In case of comparison between the measured data and the OSU91A geopotential model, the mean and the standard deviation were found to be 11.93 mGal and 19.19 mGal, respectively. The comparison of gravity anomalies obtained from the OSU91A geopotential model and the altimeter data was carried out. The results were mean of 5.30 meal and standard deviation of 19.62 mGal. From the results, we could be concluded that the gravity anomalies computed from the altimeter data is used to the geoid computation instead of the measured data.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.14 no.1
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• pp.49-58
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• 1996

This paper deals with the gravimetric solution of geoid by Fast Fourier Transform(FFT) technique in and around Korean Peninsula. The used reference surface is OSU91A geopotential model up to degree and order 180 refered to GRS80. The remove and restore technique was applied to obtain the geoidal height in this paper. And the FFT with 20% window was applied to compute the medium wavelength effect from terrestrial gravity anomalies. For the comparison of computed results, the geometric geoidal height was derived from GPS/Levelling data. According to the comparison, the mean value and RMSE of the differences are 0.3819m and 0.4695m respectively.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.4 no.1
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• pp.1-12
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• 1986

An attempt to obtain equipotential surface over the East China Sea along the three SEASAT ground tracks are described. Total correction of sea surface heights above the reference ellipsoid provided by SEASAT GDR Altimeter data consists of ocean tides and surges, body tides, sea level pressure inverse barometer effect corrections for the present study. It was shown that three equipotential surface derived from the corrections were qualitatively in agreement with GEM l0B Model and SS3 Mean Sea Surface Model.

• The Journal of the Korea Contents Association
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• v.17 no.7
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• pp.283-293
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• 2017

This study analyzed the actual conditions of use of public sports facilities and characteristics of the users of the facilities through surveys and measured the spatial imbalance of the public sports facilities currently supplied by using gravity potential model. This study also suggests evaluation criteria that may be considered for efficient location selection by examining the change of accessibility to the facilities that meet the needs of users in the future. As the results of the questionnaire survey, unlike current usage, the users hoped for badminton, weight training and swimming. And we could confirm the demand for the expansion of the multi - purpose indoor gym which can carry out such activities in the areas. As the result of the analysis on the difference in accessibility of the public sports facility, there were some large variations in the regions. It was found that a balanced supply of facilities was needed in terms of equity. In particular, when analyzing by considering the population estimates of 2025, It is analyzed that the accessibility will be reduced to about 60% compared to that of 2015. In addition, it is evaluated as the best alternative in terms of overall efficiency that the location of the facilities should be in Munsan area where population growth is expected in the future.

• Korean Journal of Remote Sensing
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• v.33 no.3
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• pp.267-274
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• 2017

The purpose of this research was to develop and present methods to detect sinkholes which can exist underneath the surface of the ground. First, we buried a water tank with dimensions $1.8{\times}0.8{\times}0.8m$ at a distance of 1.8 m from the surface. This played the role of the sinkhole. Secondly, we created a square zone with sides 12 meters away from the buried water tank. Within this zone, we measured the gravity at 1-meter intervals using a Scintrex CG5 relative gravimeter with a resolution of 0.001 mGal. Additionally, we performed three-dimensional (3-D) gravity modeling to calculate the theoretical values of the relative gravity around our model sinkhole. The resulting values for the relative gravity around the sinkhole depended on the method used. The measured effect of gravity was 0.036 mGal and the effect calculated using 3-D modeling was 0.024 mGal. Our results suggest that sinkholes that are similar in size to the water tank used in this study can be detected using relative gravity surveys. Smaller sinkholes can be detected by reducing the intervals between the relative gravity measurements.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.16 no.1
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• pp.17-26
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• 1998

This paper deals with gravimetric geoid determination by Fast Hartely transform (FHT) technique in and around the Korean peninsula. A number of data files were compiled for this work, containing now more than 69, 001 point gravity data on land and ocean areas. Especially, regression was applied to estimate gravity anomalies in the northern area of peninsula. For evaluating accuracy of geoid obtained, GPS/Leveling data of 49 stations were prepared. EGM96 global geopotential model to degree 360 was used in order to determine the long wavelength effect of geoid undulations. By applying the remove-restore technique geoid undulations were determined by combining a geopotential model, free-air gravity anomalies. Fast Hartley Transform technique is a suitable solution that uses the advanced spectral technique on the sphere. It was applied to predict geoid undulations by Stokes's integral. Accuracy of geoid undulations was evaluated by comparing with results derived from GPS/Leveling. Standard deviation of differences is about 33 cm.

• Journal of the Korean Geophysical Society
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• v.10 no.1
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• pp.13-25
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• 2007

We investigated the undulation of Moho depth and the crustal structure of the continental margin in the East Sea along the Korea Peninsula from inversion and modelling using potential data and previous seismic results. Free-air gravity anomalies generally reflect topography effect. Bouguer gravity anomalies increase toward the Ulleung Basin, indicating that Moho depth is shallower under the Ulleung Basin. Positive magnetic anomalies exist along the continental margin and decrease toward the Ulleung Basin. In analytic signal, the small anomaly in the Hupo Bank infers that the Hupo Bank is uplifted by igneous intrusion and the strong anomaly on the continental slope denotes existence of SDR(seaward dipping reflectors), which are in accordance with the location of SDR detected in previous seismic studies. The inversion result of Bouguer gravity anomaly and the 2-dimensional gravity modelling indicate that the undulation of Moho depth shallows from the continental shelf toward the Ulleung Basin. This is in good agreement with the Moho depth calculated by the previous seismic velocity model using ocean bottom seismometer(OBS). The 2-dimensional gravity modelling infers magmatic underplating zone under the lower continental crust on the continental margin of the East Sea, indicating the possible rifiting of the continental margin.

• Journal of Astronomy and Space Sciences
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• v.12 no.2
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• pp.244-255
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• 1995

The success of a satellites mission is largely depended upon the choice of an appropriate orbit. In the case of a remote sensing satellite which observes the Earth, there exits an optimum solar elevation angle depending on the mission. Therefore a sun-synchronous orbit is suitable for a remote sensing mission. The second-order theory for secular perturbation due to non-symmetric geopotential was described. To design a sun-synchronous orbit, a constraint condition on regression of node was derived. A algorithm to determine the altitude and the inclination was introduced using this constraint condition. As practical examples, the altitudes and the inclinations of four remote sensing satellites were calculated. The ground tracks obtained by the orbit propagator were used to verify the resulting sun-synchronous orbital elements.

• Journal of Astronomy and Space Sciences
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• v.6 no.2
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• pp.101-108
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• 1989

The algorithm was developed for the estimation of orbital decay of the Soviet Satellite COMOS 1402 which divides into three body-COSMOS 14020-A, B and C-and fell down early in 1983. The perturbation effects due to the nonspherical geopotential and air drag were considered and the standard atmospheric model were built for obtaining the atmospheric density as a function of the height. The orbital elements of NASA GSFC during orbital decay used in estimation of orbital decay. We compared the estimation values with the published ones of the American State Department. In the case of COSMOS 1402-C, the estimated values accorded with the published ones but, in the case of COSMOS 1402-A, the decay time and the approximated position differed respectively one minute and two degrees in both latitude and longitude from the published ones.

• Journal of Astronomy and Space Sciences
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• v.14 no.2
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• pp.381-385
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• 1997

A long-term prediction algorithm of geostationary orbit was developed using the analytical method. The perturbation force models include geopotential upto fifth order and degree and luni-solar gravitation, and solar radiation pressure. All of the perturbation effects were analyzed by secular variations, short-period variations, and long-period variations for equinoctial elements such as the semi-major axis, eccentricity vector, inclination vector, and mean longitude of the satellite. Result of the analytical orbit propagator was compared with that of the cowell orbit propagator for the KOREASAT. The comparison indicated that the analytical solution could predict the semi-major axis with an accuracy of better than $pm35$ meters over a period of 3 month.