• Asia-pacific Journal of Multimedia Services Convergent with Art, Humanities, and Sociology
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• v.6 no.12
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• pp.631-638
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• 2016

GNSS(Global Navigation Satellite System) such as GPS(Global Positioning System), GLONASS(GLObal NAvigation Satellite System) has been used in various fields for construction of geospatial inforamtion. But RTK or VRS method for high accuracy has some bad points like requirement of additional GNSS device and internet. So, this methods are difficult to take advantage of field survey. In this study, In this study, experiments using DGPS handheld devices and smart devices that can maximize mobility through was to suggest ways to improve the efficiency of field survey work. As a results, field survey work with smart devices is difficult to apply the limits of accuracy yet. On the other hand, DGPS has been found possible to determine the position accuracy within 1m. If DGPS is used in related work can greatly improve the efficiency of field survey work, which is currently much is done by hand, it is expected to serve as the basis for a structured GIS data management.

• 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 Korea Academia-Industrial cooperation Society
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• v.22 no.2
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• pp.296-301
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• 2021

GPR is used for non-destructive investigations, ground investigations, and underground facilities exploration at construction sites. In this study, the applicability to GPR exploration of water pipes linked to Network RTK was presented. Data on the water supply pipes in the study site were acquired using GPR, and the location and depth of buried water pipes could be measured. The accuracy was evaluated from the GNSS observation performance and showed a deviation of -0.16m ~ 0.15m. This satisfied the equipment performance of the public survey work regulation, suggesting that the exploration of water pipes using GPR is possible. Because GPR does not require grounding installation, as in conventional metal pipe detectors, it will increase the efficiency of work for underground facility exploration. Exploration using GPR can acquire the location and depth of metallic and non-metallic underground facilities, so it can be utilized in the construction of a GIS system. If a comparison of the exploration characteristics is carried out, it will be possible to present various uses of underground facility exploration using GPR.

• Journal of Korean Society for Geospatial Information Science
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• v.23 no.2
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• pp.39-48
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• 2015

Lately, Unmanned Aerial Vehicles(UAV), Unmanned Aerial Systems(UAS) or also often known as drones, as a data acquisition platform and as a measurement instrument are becoming attractive for many photogrammetric surveying applications, especially generation of the high density point clouds(HDPC). This paper presents the performance evaluation of a low-cost rotary wing quadrocopter UAS for generation of the HDPC in a test bed environment. Its performance was assessed by comparing the coordinates of UAS based HDPC to the results of Network RTK GNSS surveying with 62 ground check points. The results indicate that the position RMSE of the check points are ${\sigma}_H={\pm}0.102m$ in Horizonatal plane, and ${\sigma}_V={\pm}0.209m$ in vertical, and the maxium deviation of Elevation was 0.570m within block area of ortho-photo mosaic. Therefore the required level of accuracy at NGII for production of ortho-images mosaic at a scale of 1:1000 was reached, UAS based imagery was found to make use of it to update scale 1:1000 map. And also, since this results are less than or equal to the required level in working rule agreement for airborne laser scanning surveying of NGII for Digital Elevation Model generation of grids $1m{\times}1m$ and 1:1000 scale, could be applied with production of topographic map and ortho-image mosaic at a scale of 1:1000~1:2500 over small-scale areas.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.38 no.3
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• pp.259-267
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• 2020

For real-time precise positioning, N-RTK (Network Real-Time Kinematic) technology is widely used these days. However, the currently operating N-RTK system has a limitation in terms of the number of users. Therefore, if reference points generate correction messages with no limit on the number of users are developed later, it is determined that an appropriate reference point installation interval is required, so that the accuracy of the N-RTK system according to the baseline distance was analyzed. This experiment utilized receivers with varying performance that estimated the rover position, and RTKLIB, an open-source software, is used for processing data. As a result, the rover position was estimated accurately with a high rate of fixed ambiguity for all the receivers. When the reference station with a baseline length of 40 km was used, the vertical RMSE (Root Mean Squared Error) was quite similar to the short baseline case, but only half of the ambiguity fixing rate was achieved. The outlier in the estimated rover position was not observed for the longer baselines in the case of a high-end receiver. It is necessary to analyze the ambiguity fixing and the accuracy of the kinematic positioning with scientific GNSS processing software.

• Journal of Positioning, Navigation, and Timing
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• v.7 no.4
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• pp.295-305
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• 2018

Network RTK is a highly practical technology that can provide high positioning accuracy at levels between cm~dm regardless of user location in the network by extending the available range of RTK using reference station network. In particular, unlike other carrier-based positioning techniques such as PPP, users are able to acquire high-accuracy positions within a short initialization time of a few or tens of seconds, which increases its value as a future navigation system. However, corrections must be continuously received to maintain a high level of positioning accuracy, and when a time delay of more than 30 seconds occurs, the accuracy may be reduced to the code-based positioning level of meters. In case of SSR, which is currently in the process of standardization for PPP service, the corrections by each error source are transmitted in different transmission intervals, and the rate of change of each correction is transmitted together to compensate the time delay. Using these features of SSR correction is expected to reduce the performance degradation even if users do not receive the network RTK corrections for more than 30 seconds. In this paper, the simulation data were generated from 5 domestic reference stations in Gunwi, Yeongdoek, Daegu, Gimcheon, and Yecheon, and the network RTK and SSR corrections were generated for the corresponding data and applied to the simulation data from Cheongsong reference station, assumed as the user. As a result of the experiment assuming 30 seconds of missing data, the positioning performance compensating for time delay by SSR was analyzed to be horizontal RMS (about 5 cm) and vertical RMS (about 8 cm), and the 95% error was 8.7 cm horizontal and 1cm vertical. This is a significant amount when compared to the horizontal and vertical RMS of 0.3 cm and 0.6 cm, respectively, for Network RTK without time delay for the same data, but is considerably smaller compared to the 0.5 ~ 1 m accuracy level of DGPS or SBAS. Therefore, maintaining Network RTK mode using SSR rather than switching to code-based DGPS or SBAS mode due to failure to receive the network RTK corrections for 30 seconds is considered to be favorable in terms of maintaining position accuracy and recovering performance by quickly resolving the integer ambiguity when the communication channel is recovered.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2020.11a
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• pp.159-160
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• 2020

카메라, 라이다, RTK-GNSS 등의 센서는 자율주행 YT 기술 개발을 위해 매우 주요한 요소이다. 본 연구에서는 항만 터미널의 무인화에 핵심 기술 중의 하나인 자율주행 YT에서 안전한 자율주행을 실현하기 위한 다중센서 기반의 융합인식 기술을 제안하고자 한다.

• Journal of The Geomorphological Association of Korea
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• v.28 no.4
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• pp.41-52
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• 2021

With the popularization of drones and the ease of use of the Global Navigation Satellite System (GNSS), drone photogrammetry for terrain information has been widely used. Drone photogrammetry enables the realization of high-accuracy three-dimensional topography for the entire area with less effort and time compared to the past direct survey using GNSS or total station. From 3-D topographic data, various topographical analysis is possible. To improve the accuracy of drone photogrammetry, direct GCP surveying in the field is essential, and the numbers and reasonable positioning of GCPs are very important. In the case of beaches or tidal flats on the west coast of Korea, the numbers and location of GCPs are important factors in efficient drone photogrammetry because of the size of the area, difficulties of movement, and the risk from tides. If the RTK (Real-time kinematic) or PPK (Post-processed kinematic) method is used, the increased accuracy of the drone's location enables high-accuracy photogrammetry with a small number of GCPs. This study presents an efficient drone photogrammetry method in terms of time and economy by comparing and analyzing the results of drone photogrammetry using Non-PPK with low-cost PPK-Kit, based on the tests of various numbers and locations of GCPs in the university field including various slopes and structures like coastal terrain.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.31 no.2
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• pp.135-142
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• 2013

Recently, it is a pretty well known way to compute GPS/INS using Continuously Operating Reference Station (CORS) and Network-based RTK for obtaining Exterior Orientation (EO) parameters of aerial photogrammetry. In this study, it is way to compute Exterior Orientation (EO) parameters using ground base stations, using Continuously Operating Reference Station (CORS) broadcast orbits and International GNSS Service (IGS) rapid orbits. And the residuals of Exterior Orientation (EO) parameters were computed based on the results of ground base station. As a result, the case of using SmartBase to obtain Exterior Orientation (EO) parameters was showed the high accuracy of X, Y, K more than using Continuously Operating Reference Station (CORS) of National Geographic Information Institute (NGII). Also, distance and direction of Continuously Operating Reference Station (CORS) of National Geographic Information Institute (NGII) from ground base station affected Exterior Orientation (EO) parameters. And different forms of residuals were shown according to the aerial photo courses.

• Proceedings of the Korea Water Resources Association Conference
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• 2021.06a
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• pp.33-33
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• 2021

예측하기 어려운 복잡한 기후 변화로 인해 수자원 관리측면에서 다양한 방법을 도입하여 해결할 수 있는 방안이 국가적 주요 관심사로 다루어지고 있다. 따라서 투입인력과 소요시간 절감, 장비와 인력진입 불가지역에 대한 정보획득, 높은 공간해상도, 항공측량 대비 높은 경제성 등 다양한 장점의 드론을 이용한 하천지형 특성별 수리특성 분석방안이 필요하다. 본 연구에서는 성연천 하류부지역을 대상으로 위성항법시스템(Global Navigation Satellite System, GNSS) 측량 지형성과와 드론측량(Drone) 지형성과를 지상에 설치된 CHP(Check Point) 좌표 값을 확인하여 두 지형의 정확도를 비교하였으며 HEC-RAS 모형을 이용하여 빈도별 수리특성을 비교 산정하였다. 본 연구는 성연천 하류 480m구간을 선정하고 GNSS를 이용한 실측지형자료와 GCP(Ground Control Point)를 얻기 위해 정확도 검증을 실시하였으며 위성항법시스템(GNSS) 측량과 DRONE RGB측량의 CHP(Check Point) 오차를 비교하여 정확도를 검증하였다. 오차 값이 확인된 위성항법시스템(GNSS)을 이용하여 가상기준점을 선정하고 RTK 모바일스테이션을 설치하여 DRONE LIDAR측량을 통해 지형자료를 취득하였으며 얻어진 지형자료를 HEC-RAS를 통해 입력 후 성연천 하천기본계획에 제시되어진 조도계수와 빈도별 홍수위를 적용하여 연구구간 480m에 대해 100년 빈도의 결과 값을 비교 검토하였다. 100년 빈도 계획 홍수량 조건의 하상과 한계수위의 차에서 위성항법시스템(GNSS) 측량 지형자료를 기준으로 평균수위 측정오차는 드론 RGB 측량 지형자료 0.460m, 드론 LIDAR 측량 지형자료 0.260m의 결과를 얻었으며 동일 조건 흐름하의 평균유속에서 위성항법시스템(GNSS) 측량 지형자료를 기준으로 평균유속 측정오차는 드론 RGB 측량 지형자료 0.40m/s, 드론 LIDAR 측량 지형자료 0.36m/s의 결과를 얻었다. 통수 단면적의 비교 결과는 위성항법시스템(GNSS) 측량 지형자료를 기준으로 드론 RGB 측량 지형자료 전체 단면의 평균오차는 20.20m², 드론 LIDAR 측량 지형자료 전체 단면의 평균오차는 21.68²의 결과를 얻었으며 이상에서와 같이 홍수위와 평균유속, 통수 단면적의 측정오차 비교 결과를 종합할 때 통수 단면적 측정결과는 위성항법시스템(GNSS) 측량과 드론 RGB 측량의 차이가 적었으나 계획 홍수량 조건의 하상과 한계수위 차이와 동일조건 흐름하의 평균유속에서 위성항법시스템(GNSS) 측량과 드론 LIDAR 측량의 차이가 적은 것으로 나타났다. 그리고 통수용량(capacity)(m³) 비교에서는 위성항법시스템(GNSS) 측량을 기준으로 드론 RGB 측량은 약 7644m³, 드론 LIDAR 측량은 약 7547m³의 차이를 보여 드론 LIDAR를 이용한 결과가 가장 정확한 측정방법으로 추천할 수 있음을 확인하였다.