• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.29 no.4
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• pp.393-403
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• 2011

In this study, we suggested the period of tide observations is proper to calculate the mean sea level(MSL) precisely on Incheon tide station using wavelet analysis, and newly determined then the vertical reference surface of Korea using the calculated MSL. In order to calculate the height difference between the calculated MSL and specific ground station (ICGP) near the Incheon tide stations, we performed the laser measurements directly to the sea surface where located below ICGP. The orthometric-height of ICGP was determined that corrected the height difference to the calculated MSL using linear interpolation method. Finally, we connected the orthometric-height of ICGP with the original benchmark (ORBM) using GPS leveling methods for determining the new orthometric-height of ORBM. As the results, there is a variation amount of 0.026m between the new MSL was calculated in this study and old MSL was calculated in 1910's. Also, there is a difference of 0.035m between the new and old orthometric-heights of ORBM. The connection (or leveling) error of 0.009m was revealed in new orthometric height of ORBM with consideration of MSL variation which may caused by the error of GPS ellipsoid height and/or geoid model. In this study, we could be determined precisely the orthometric-height of ORBM based on the new MSL of Incheon Bay using only GPS leveling method, not a spirit leveling method. Therefore, it is necessary to determine the vertical datum strictly using long-term and continuously tide observations more than 19 years and to use the GPS leveling method widely in the height leveling work for the effective changeover from the orthonormal to the orthometric in national height system.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.13 no.2
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• pp.285-289
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• 1995

This paper describes the determination of geoid using height data measured by GPS and Spirit Levelling. The GPS data of the 88 stations were used to determine the geoid undulation (N) which can be easily obtained by subtracting the orthometric height(H) from the ellipsoidal height(h). From the geoid undulation (N) calculated at each station mentioned above, geoid plots with a contour interval of 0.25 m were drawn using two interpolation methods. The following interpolation methods were applied and compared with each other: Minimum Curvature Method and Least Squares Fitted Plane. Comparison between geometric geoid and gravimetric geoid undulation by FFT technique was carried out.

• Journal of Korean Society for Geospatial Information Science
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• v.3 no.2 s.6
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• pp.75-82
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• 1995

The calculation of astronomic latitude and longitude have been carried by astrolabe, theodolite. Conventional procedures to determine it require clear weather conditions, time high cost. So we need more effective method to decide them. The objective here is to present method to computate astronomic latitude and longitude by mixing GPS observation result and geodetic height. Also to decide geodetic height we used GPS/leveling, DMA(n=m=180) and OSU91A(n=m=360) methods. Compared to conventional procedures we could obtain astronomic latitude and longitude using GPS by $1{\sim}3'$ difference. If the precise geoid model of Korea will be developed, we can compute astronomic latitude and longitude effectively using GPS observation only.

• 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.19 no.2
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• pp.155-161
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• 2001

When determining a three dimensional position for engineering purposes, we can use the GPS survey to find position. According to the enhancement of precision for domestic Geoid model, the positional accuracy of GPS about precise method of vertical position has been also increased. But by considering Geoid undulation, it is difficult to measure GPS-derived elevations. Because Geoid undulation has changed little in local sites, GPS-derived elevations are similar to orthometric height. By ignoring Geoid undulation, it is possible to measure GLT-derived elevations at the local. small construction sites. GLT(GPS Leveling Technique) provides a method for computing orthometric heights. GLT processes the data more rapidly than conventional measurement devices. We only considered the weight factors affecting accuracy between the points. That is, the GPS procedures to produce satisfactory elevation accuracy depends on the method of observations, receivers and conditions of the local environment. A comparison was performed between the GPS survey using Geoid model and GLT at a part within Pusan National University and construction model sites in South Korea. And the writers proved the GPS surveying is efficient in positioning accuracy, time, and cost on a construction sites.

• 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 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 Cadastre & Land InformatiX
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• v.48 no.2
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• pp.99-108
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• 2018

The purpose of this study is to determine the precise height in mountainous areas of South Korea and Jiri mountain area was selected as a test bed for the study. Gravity observation and GNSS surveying were performed for 44 BM(Benchmark) points in the test bed and calculate the height and the height correction. In the calculation, the dynamic correction amount, the orthometric correction amount and the normal correction amount were calculated, and the dynamic height and orthometric height and the normal height were calculated considering each correction amount. The results showed that the difference between normal gravity and observed gravity and also the difference between orthometric correction and the normal correction. In addition, the results of the comparison of the present official BM height and the computed orthometric height in this study show that Korean height system should be shifted from the normal orthometric height system to the orthometric height system. Because the difference between the orthometric correction and the normal correction within the test bed indicated a distribution of at a minimum of -234.41 mm up to 196.925 mm, and the difference between the present official BM height and the calculated orthometric height were distributed from -0.121m to 0.011 m.

• 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.