• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.27 no.3
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• pp.303-310
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• 2009

We processed seven years data of 142 IGS(International GNSS Service) stations were processed, which have been selected with an optimal network algorithm, to realize terrestrial reference system. To verify the result, a comparison with the ITRF2005 was given both in positions and velocities with transformation parameters estimation. The transformation parameters are within 4.3 mm in length, while the RMS(root mean square) difference of positions and velocities are 6.7 mm and 1.3 mm/yr in horizontal and 13.3 mm and 2.4 mm/yr in vertical, respectively, which represent good coincidences with ITRF2005. This research would help developing our own geodetic reference frame and may be applied for the global earth observations such as the global tectonics. A further improved TRF would be expected by applying various data processing strategies and with extension of data in number and observation period.

• Journal of Korean Society for Geospatial Information Science
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• v.23 no.3
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• pp.31-39
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• 2015

This paper presents the static and kinematic positioning accuracy by the real-time GPS positioning modes of the low-cost GPS receivers using NTRIP-based augmentation service. For this, acquires both the raw measurements data of the field tests by LEA 6T GPS module of u-blox AG, and correction communication via NTRIP caster with RTKLIB as an open source program for GNSS solution. With computing the positions of the check points and road tracks by six kinds of GPS positioning modes which are Single, SBAS, DGPS, PPP, RTK, and TCP/IP_RTK, compared these results to the reference position of the check points. The position error average and rmse of the static test by GPS L1 RTK surveying showed $N=0.002m{\pm}0.001m$, $E=0.004m{\pm}0.001m$ in horizontal plane, and $h=-0.116m{\pm}0.003m$ in vertical, these results are very closed to the coordinates with the geodetic receiver. Especially, in case of the kinematic test with obstacles located on both sides of road, the computed track with ambiguity fixing showed very similar trajectory considerably from VRS network RTK mode. And also, evaluate and verify the performance of the TCP/IP_RTK mode developed based on TCP/IP protocol.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.37 no.1
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• pp.1-7
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• 2019

In this study, we estimated the tropospheric delay of GNSS (Global Navigation Satellite System) signals during passing through the atmosphere in relation to weather and seasonal factors. For this purpose, we chose four CORS (Continuously Operating Reference Station) stations from inland (CCHJ and PYCH) and on the coast (GEOM and CHJU). A total of 48 days for each station (one set of data for each week) were downloaded from the NGII (National Geographic Information Institute) and processed it using the scientific GNSS software. The average tropospheric delays in winter are less than 2,400 mm, which is about 200 mm less than those in summer. The estimated tropospheric delay shows a similar pattern from all stations except the absolute bias in magnitude, while a large delay was observed for the station located on the coast. In addition, the delay during the day was relatively stable in winter, and the average tropospheric delay was strongly related to the orthometric height. The inland stations have tropospheric delays by the precipitation rather than humidity due to dry weather and difference in temperature. On the contrary, it was primarily caused by the humidity on the sea. The correlation between temperature and water vapor pressure is 0.9 or larger for all stations, and the tropospheric delay showed a high linear relationship with temperature. It is necessary to analyze the GNSS data with higher temporal resolution (e.g. all RINEX data of the year) to improve the stability and reliability of the correlation results.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.40 no.3
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• pp.207-215
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• 2022

This research has been focused on accessing precision and accuracy of UAV (Unmanned Aerial Vehicle)-derived 3-D surveying coordinates. To this end, a highly precise and accurate testing control network had been established by GNSS (Global Navigation Satellite Systems) campaign and its network adjustment. The coordinates of the ground control points and the check points were estimated within 1cm accuracy for 95% of the confidence level. FC330 camera mounted on DJI Phantom 4 repeatedly took aerial photos of an experimental area seven times, and then processed them by two widely used software packages. To evaluate the precision and accuracy of the aerial surveys, 3-D coordinates of the ten check points which automatically extracted by software were compared with GNSS solutions. For the 95% confidence level, the standard deviation of two software's result is within 1cm, 2cm, and 4cm for the north-south, east-west, and height direction, and RMSE (Root Mean Square Error) is within 9cm and 8cm for the horizontal, vertical component, respectively. The interest is that the standard deviation is much smaller than RMSE. The F-ratio test was performed to confirm the statistical difference between the two software processing results. For the standard deviation and RMSE of most positional components, exception of RMSE of the height, the null hypothesis of the one-tailed tests was rejected. It indicates that the result of UAV photogrammetry can be different statistically based on the processing software.

• Bulletin of the Korean Space Science Society
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• 2011.04a
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• pp.19.1-19.1
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• 2011

국가기상위성센터는 2013년 태양활동 극대기를 대비하고 천리안 위성의 안정적인 운영을 위하여 우주기상업무를 추진하고 있다. 2009년에 수행된 우주기상업무 기본계획 수립을 위한 기획연구를 시작으로, 2010년에는 국내 GNSS 자료를 준실시간으로 수집하여 총전자밀도(TEC)를 산출하는 시스템을 개발하였으며, 외국 우주기상 자료를 수집하여 태양 영상을 비롯한 우주환경인자를 실시간으로 제공하기 위한 우주기상 테스트베드를 시험운영하고 있다. 또한 대국민 우주기상 서비스를 위한 우주기상 예측모델 개발을 5개년에 걸쳐 단계적으로 진행하고 있다. 미국의 NOAA-SWPC, NASA-GSFC와 같은 우주기상 선진기관들과의 2013년 태양활동 극대기에 대비한 우주기상 감시, 예측모델 및 예보서비스에 대한 활발한 교류 협력을 통해 기상청의 우주기상예보 역량을 늘려나갈 계획이다.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.28 no.1
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• pp.13-20
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• 2010

Currently, GPS data process software appears different results that according to user's skills or software. Also, lots of time and efforts are necessary for using GPS data process software to general user, not a specialist On the other band, on-line GPS data process service have a merit that can cony out GPS data process without technical efforts and time. In this study, permanent GPS site's observation data of NGII(National Geographic Information Institute) was processed by on-line GPS data process service, and utilization assessment of on-line GPS data process service was performed by comparing this result with notified coordinates by the NGII in order to analyze positional accuracy. 10 permanent GPS sites of NGII including Suwon which is registered in IGS(International GNSS Service) were selected and these GPS observation data was processed by AUSPOS and CSRS-PPP.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.36 no.4
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• pp.245-254
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• 2018

Impact of tropospheric correction techniques on accuracy of the GPS (Global Positioning System) derived ellipsoidal heights has been experimentally assessed in this paper. To this end, 247 baselines were constructed from a total of 88 CORS (Continuously Operating Reference Stations) in Korea. The GPS measurements for seven days, acquired from the so-called integrated GNSS (Global Navigation Satellite Systems) data center via internet connection, have been processed by two baseline processing software packages with an application of the empirical models, such as Hopfield, modified Hopfield and Saastamoinen, and the estimation techniques based on the DD (Double-Differenced) measurements and the PPP (Precise Point Positioning) technique; hence a total number of the baseline processed and tested was 8,645. Accuracy and precision of the estimated heights from the various correction schemes were analyzed about baseline lengths and height differences of the testing baselines. Details of these results are summarized with a view to hopefully providing an overall guideline of a suitable selection of the modeling scheme with respect to processing conditions, such as the baseline length and the height differences.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.12
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• pp.411-416
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• 2020

Field investigations of forests are carried out by writing measured data by hand, and it is a hassle to reorganize the results after a field survey. In this study, a method using object modeling and augmented reality (AR) was applied in a test forest to increase the efficiency of a field investigations. Using a 3D laser scanner, data on were acquired 387 trees within an area of 1 ha at the study site. The coordinates, height, and diameter were calculated through object extraction and modeling of a tree. The proposed can reduce the time required to acquire data in the field and can be used as basic data for building related systems. In addition, the modeling results of trees and a survey using GNSS and AR techniques can be used check coordinates, labor, and attribute information, such as the chest height diameter of the trees being surveyed in the field. The shortcomings of the survey method could be improved. In the future, the method could greatly improve the efficiency of tree surveys and monitoring by reducing the manpower and time required for field surveys.

• Journal of Space Technology and Applications
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• v.4 no.3
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• pp.210-219
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• 2024

This study investigates various ionospheric and thermospheric disturbances around the Korean Peninsula during the G5 geomagnetic storm occurred on May 10, 2024. This level of storm was the first of its magnitude in 21 years, resulting in auroras visible even in South Korea and severe space weather worldwide. The Korea Astronomy and Space Science Institute has been providing ionospheric information over Korea through total electron content (TEC) measurements from the Global Navigation Satellite System (GNSS) and monitoring the impact of ionospheric disturbances on GNSS signals by operating five GNSS scintillation stations in Korea and other countries. During this storm period, large amplitudes of TEC variations were observed over South Korea, along with anomalous TEC enhancements accompanied by strong scintillations at night and persistent TEC depletion on the dayside during the storm's recovery phase. Such daytime TEC depletion disturbances are quite rare, typically occurring only a few times throughout the 11-year solar cycle. While the association of persistent TEC depletion during the daytime with neutral composition disturbances was identified through observations, the causes of TEC enhancement and strong scintillation at night remain unclear. We speculate that the uplift of the ionosphere by storm-induced electric fields is responsible for the TEC enhancement and scintillation, but this hypothesis requires validation based on additional observational data.

• Journal of the Korean Association of Geographic Information Studies
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• v.27 no.3
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• pp.30-42
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• 2024

In this paper, we presented the processing process of the sea floor mapping system using multi-beam echo-sounding data through actual measurements and the results of processing the multi-beam echo-sounding data obtained by exploring some waters of Yeosu Bay. Simultaneously and continuously observe the location and water depth of the sea using GNSS and multi-beam echo sounder, synchronization of the two data, depth correction process considering the tide level at the time of observation, 3D model of the seafloor, contour map, and longitudinal and cross-section data of the seafloor topography. In addition, by extracting efficiently the dredging volume according to the dredging area and planned water depth required for dredging construction management of submarine projects, it can be used for maintenance and management of marine construction sites and ports.