• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.30 no.4
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• pp.343-352
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• 2012

In order to precisely determine the vertical displacements of CORS antenna phase centers caused by their replacement, intensive research has been carried out in this paper throughout processing GPS measurements made before and after the events. After applying the estimated displacement in the data processing, results show that coordinate repeatability of the vertical component is able to be 7.9mm on average. Comparing with results (e.g., 23.5mm) without applying the displacement, it was possible to conclude that these accuracies are significantly improved, which is equivalent to those before the event of the replacement.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.33 no.5
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• pp.343-351
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• 2015

It is well-known that even the DGNSS (Differential Global Navigation Satellite System) technique in navigation for ground vehicles can only provide several meters of accuracy, such that it is suitable for simple guidance. On the other hand, centimeter to millimeter level accuracy can be obtained by using carrier phase observables in the field of precision geodesy/surveying. In this study, a preliminary study was conducted to apply NRTK (Network-RTK) by NGII (National Geographic Information Institute) to ground vehicle navigation. Onboard GNSS receivers were used for NRTK throughout the country, and the applicability of NRTK on navigation was analyzed based on NRTK surveying results. The analysis shows that the overall ambiguity fixing rate of NRTK is high and is therefore possible to apply it for navigation. In urban areas, however, the fixing rate decreases sharply, therefore, it needs to employ a method to minimize the effect of the float solutions, which can reach up to 10 meters. It is still feasible to obtain a centimeter level of accuracy in some area using NRTK under certain conditions. But, the ambiguity fixing rate of FKP falls down to 55% for high speed vehicles, and so the surveying accuracy should be determined by considering various factors of surveying environments. In addition, it is difficult to fix ambiguities using single-frequency GPS receivers. Finally, several suspicious NRTK(FKP) connection problems occurred during atmospheric disturbances (phase two or up), which should be investigated further in upcoming research.

• 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.23 no.4
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• pp.385-392
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• 2005

This paper describes an accuracy analysis of newly developed gravimetric geoid and an improvement of developed geoid using GPS/Levelling data. We developed the KGEOID05 model corrected with the correction term. The correction term is modelled using the difference between GPS/Levelling derived geoidal heights and gravimetric geoidal heights. The stochastic model used in the calculation of correction term is the least squares collocation technique based on second-order Markov covariance function. 373 GPS stations were used to model the correction term. The standard deviation of KGEOID05 is about 11 cm and it indicates that we can be determined accurate heights ($2{\sim}3\;cm$) when we made precise modelling using KGEOID05 and a few GPS measurements for the local area.

• Journal of the Korean Association of Geographic Information Studies
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• v.26 no.4
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• pp.56-66
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• 2023

Safety accidents are increasing, such as changes in groundwater levels due to construction work or natural influences, or ground cave-ins caused by soil runoff from old water supply and sewage pipes. In addition, underground facility management agencies must make efforts to improve the accuracy of underground information through continuous investigation and exploration in accordance with the Special Act on Enhanced Underground Safety Management. Accordingly, in this study, we defined the configuration of equipment and data processing method to collect 3D precise exploration underground facility information and developed 3D underground facility information collection technology to ensure accuracy of underground facilities. As a result of verifying the developed technology, the horizontal accuracy improved by an average of 6cm compared to the existing method, making it possible to acquire 3D underground facility information within the error range of the public survey work regulations.

• 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.

• Journal of the Korean Society for Railway
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• v.10 no.6
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• pp.685-691
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• 2007

In this paper through Honan high-speed railroad which is planned with the north and south axis, we will verify the feasibility of the coordinate conversion using railroad control points after regarding current planned-railroad as the linear central axises. From analysis, distortion of Y axis varies 21 cm to 40 cm diminishing to a gentle straight line, distortion of X axis varies 14 cm to 29 cm. Through a revision, the deviation value between the coordinates were 6 mm to 9 mm and it satisfied the allowable error of national geographic information institute which is following ITRF (International Terrestrial Reference Frame) and cadastral boundary survey (10 cm). consequently the coordinate conversion is possible using railroad control points as common control points.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.3 no.4
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• pp.228-233
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• 1998

This study presents a close-range photogrammetry that is applicable to beach profile estimation using a non-metric camera. Based on the analysis of oblique video image in which the video camera was installed on a horizontal plane and the field of view was fixed, a new equation to analyze a photograph was developed considering the following aspects: (1) camera is allowed to be rotated about its optical axis and (2) a simple error model is adopted to correct lens distortion and other systematic errors associated with the non-metric camera, which improves accuracy of non-metric imageries. To test the modified technique, photographs of the beach were taken near the Donghae City in February, 1998. In addition, beach profiles were surveyed with conventional dumpy level and surveying staff. RMS error between the estimated and measured beach profiles is less than 10 cm in elevation.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.34 no.1
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• pp.79-90
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• 2016

The study has purposed in evaluating experiences for achievable accuracy and precision of time series at 3-D coordinates. It has been estimated from the kinematic medium-range baseline processing of Continuously Operating Reference Stations (CORS) for the potential application of crustal displacement analysis during an earthquake event. To derive the absolute coordinates of local CORS, it is highly recommended to include some of oversea country references, since it should be compromised of an observation network of the medium-range baselines within the length range from tens of kilometers to about 1,000 kilometers. A data processing procedure has reflected the dynamics of target stations as the parameter estimation stages, which have been applied to a series of experimental analysis in this research at the end. From the analysis of results, we could be concluded in that the subcentimeters-level of positioning accuracy and precision can be achievable. Furthermore, the paper summarizes impacts of satellite ephemeris, data lengths and levels of initial coordinate constraint into the positioning performance.

• Journal of Korean Society for Geospatial Information Science
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• v.23 no.2
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• pp.97-104
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• 2015

Due to the introduction of various IT devices, including the recently smartphones and the widespread use of the car navigation system to the location-based information service space has been increased. Spatial information users have been requiring higher levels of quality. In this paper, we study how to build accurate three-dimensional space information by integrating MMS(Moblie Mapping System) survey and airborne survey data. Thus, to analyze the tendency of deviation between the MMS survey and airborne survey data observed in the experimental region, the deviation tendency of the data, it was confirmed that was not consistent. Deviation correction model to select how to change the georeferencing information directly contained in the GPS/INS processing results for the determination, classifies the standard is a method for acquiring the correction reference point coordinates using the calibration model, and analyzed their advantages and disadvantages. With the information of the reference point obtained by airborne photograph of a project, using the method of correcting the MMS survey data. Not only clear the deviation existing between the MMS survey data, it was possible to confirm that the deviation exists between the airborne survey data and MMS survey data was also almost erased.