• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.14 no.6
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• pp.69-77
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• 2000

In this paper, the effects of the positions of the potential and current probes on the measurements of the ground resistance and potential gradients with the fall-of-potential method are described and the testing techniques to minimize the measuring errors are proposed. The fall-of-potential method is theoretically based on the potential and current measuring principle and the measuring error is primarily caused by the position and ground resistance of the measuring probes. The ground resistance is calculated by applying the 61.8% and rule in the fall-of-potential method, and then the potential probe is located on the straight line between the grounding electrode to be measured and the current probe. However, sometimes the grounding electrode to be measured and the measuring probes in on-site test might not be arranged on the straight line with adequate distance because there are building, road block, construction and other establishments. Provided that the grounding electrode to be measured and the measuring probes ar out of position on the straight line or have inadequate distance, the measurement of the ground resistance classically falls into an error and the measured ground resistance should be corrected. Measurements were focused on the grounding electrode system made by the ground rods of 2.4m long. It was found that the suitable separation between the grounding electrode to be measured and the current probe is more than 5 times of the length of the grounding electrode to be measured.

• Spatial Information Research
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• v.15 no.2
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• pp.111-121
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• 2007

The GPS positioning offer 3D position using code and carrier phase measurements, but the user can obtain the precise accuracy positioning using carrier phase in Real Time Kinematic(RTK). The main problem, which RTK have to overcome, is the necessary to have a reference station(RS) when using RTK should be generally no more than 10km on average, which is significantly different from DGPS, where distances to RS can exceed several hundred kilometers. The accuracy of today's RTK is limited by the distance dependent errors from orbit, ionosphere and troposphere as well as station dependent influences like multipath and antenna phase center variations. For these reasons, the author proposes Network based GPS Carrier Phase Differential Positioning using Multiple RS which is detached from user receiver about 30km. An important part of the proposed system is algorithm and software development, named DAUNet. The main process is corrections computation, corrections interpolation and searching for the integer ambiguity. Corrections computation of satellite by satellite and epoch by epoch at each reference station are calculated by a Functional model and Stochastic model based on a linear combination algorithm and corrections interpolation at user receiver are used by area correction parameters. As results, the users can obtain the cm-level positioning.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.19 no.11
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• pp.2569-2575
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• 2015

Network RTK generally uses a linear interpolation method by using the corrections from reference stations. This minimizes the spatial decorrelation error caused by the increase of distance between the reference station's baseline and user's baseline. However, tropospheric delay, a function of the meteorological data can cause a spatial decorrelation characteristic among reference stations within a network by local meteorological difference. A non-linear characteristic of tropospheric delay can deteriorate Network RTK performance. In this paper, the modeling of tropospheric delay irregularity is made from the data when the typhoon is occurred. By using this modeling, analyzing the effect of meteorological difference between reference stations on correction is performed. Finally, we analyze an effect of non-linear characteristics of tropospheric delay among reference stations to Network RTK user.

• Journal of Advanced Navigation Technology
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• v.22 no.6
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• pp.577-584
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• 2018

GNSS based transport infrastructure cluster is to broadcast satellite navigation correction information and integrity information capable of precise positioning for land transport users. This makes it possible to do lane-level positioning reliably. However, in order to provide the lane-level positioning and correction information service nationwide, new station sites selection and to build GNSS stations have a heavy cost and a burden for a considerable period of time. In this paper, we propose the cluster design criteria and national-wide network-based precise positioning for land transportation (NETPPI-LT) cluster design for a cluster-based precise positioning. Furthermore, it is analyzed the precise positioning pre-performance of this cluster design based on the spatial error and verified its suitability as the precise positioning pre-performance of the cluster design.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2004.04a
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• pp.83-87
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• 2004

본 연구는 고해상도의 충적층 지하수위 분포 조사를 위한 탄성파 굴절법 조사 방법을 소개하고 부여 군수리 충적층 일대에서 이 기법을 통해, 획득된 실제 충적층내의 지하수위 조사 결과를 제시한다. 기본적으로 본 연구에서 활용된 연속 굴절파 중합 방식은 동일 공심점(common mid point, 이후 CMP)을 갖는 굴절파 신호를 취합하고, 이격 거리(offset)에 대한 시간 지연 효과 보정을 수행한 후, 이들 신호를 중합하여, 충적층의 지하수위면에서 굴절된 신호를 보다 뚜렷이 부각시켜 정확한 지하수위 정보를 획득 하는 방식으로 일명 CMP 굴절법이라고도 한다. 이 방식은 독일에서 최초 개발되었으나(Gebrande, 1986; Orlowsky 등, 1998), 국내에서 적용되기는 본 연구가 최초이다. 이러한 탄성파의 굴절 신호를 사용하는 방식은 우선, 기존의 일반적인 고해상도 반사법 탐사에서 잡음으로 여겨졌던 굴절파 신호를 활용할 수 있으며, 고해상도 반사법 탐사와 동일한 배열과 운영 방식으로 획득된 자료에서 원하는 정보를 획득할 수 있으므로, 고해상도 반사법에 의한 기반암 조사와 함께 적용될 경우, 정화한 충적 대수층의 분포를 조사할 수 있게 하여주는 획기적인 조사 신기술이다. 개발된 기법은 부여 군수리 충적층 지역을 대상으로 적용되었으며, 그 결과 기존의 어떠한 지구물리 조사 방법보다 정확하고 분명한 지하수위 분포를 보여주었다.

• Proceedings of the Korean Society of Computer Information Conference
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• 2014.07a
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• pp.427-428
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• 2014

화재발생 시 인명 안전을 위하여 초기의 화재감지가 매우 중요한 요인이다. 기존 연기감지기의 경우 일정한 조건만 맞으면 작동하기 때문에 비화재보의 우려가 높다. 특히 차량 매연도 연료가 연소되어 나오는 연기이므로 차량정체 시 트럭 등에서 발생하는 심한 매연에도 반응하여 오작동의 가능성이 높다. 이러한 기존 화재감지기의 문제점을 해결하기 위해 다양한 IR 레이저 기반 연기검출장치가 활용되고 있다. 하지만 IR 레이저 기반 연기검출장치는 100m 거리가 이격된 레이저 발광부와 수광부 구조에 따라 발광부 레이저광선의 각도변화에 따른 수광부 레이저 포인트 위치가 매우 민감하게 변화함에 따라 초기 레이저 포인트의 초점을 정확히 정합하고, 이후 보정하기 위한 고정밀 자동 초점 정합장치가 필요하다. 이에 본 논문에서는 레이저 투광부와 수광부를 분리하여 레이저 송신기, 수신기로 구성되는 고정밀 자동초점 정합장치를 설계하고자 한다.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2014.10a
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• pp.499-500
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• 2014

화재발생 시 인명 안전을 위하여 초기의 화재감지가 매우 중요한 요인이다. 특히 도로터널, 지하철역사 등 광범위 폐쇄공간에서 연기에 의한 질식사 등 2차 피해의 발생위험이 높다. 이에 최근 광범위 공간에서 적외선 레이저를 활용한 원거리 연기검출 화재탐지기에 대한 연구가 진행되고 있다. 이러한 레이저 기반 원거리 연기검출장치는 이격(100m 이상) 설치되는 레이저 발신기와 수신기의 레이저 포인트가 정확히 정합되어야 한다. 아울러, 레이저 발신기와 수신기 사이의 거리에 비례하여 레이저 초점의 이동거리가 매우 민감하게 변화하므로 이를 정확히 정합하기 위한 고정밀 제어장치가 필요하다. 따라서 본 논문에서는 복수개의 레이저 발신모듈과 복수개의 조도센서(CdS)를 통해 초점의 정합을 자동 추적할 수 있는 알고리즘을 설계, 구현하였다. 이는 초기 레이저 초점의 설정과 이후 외부환경에 따른 초점의 틀어짐을 자동 보정하여 다양한 레이저 인식 장치에 적용될 것으로 사료된다.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.41 no.2
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• pp.133-141
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• 2021

The probe vehicle penetration rate is a required parameter in the estimation of entire volume, density, and queue length from probe vehicle data. The previous studies have proposed estimation methods without point detectors, which are based on probability structures for the locations of probe and non-probe vehicles; however, such methods are poorly suited to the case of multi-lane streets. Therefore, this study aimed to estimate the probe vehicle penetration rate at a multi-lane intersection and introduce a probability distribution of the queue length of each lane. Although a gap between estimates and observations was found, the estimates followed the trend of observations; the estimation could be improved by the correction factor hereafter. This study is expected to be used as a basic study for the estimation of entire volume, density, and queue length at multi-lane intersections without point detectors.

• Korean Journal of Remote Sensing
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• v.38 no.6_1
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• pp.1125-1139
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• 2022

In an unmanned aerial vehicles (UAVs) system, a physical offset can be existed between the global positioning system/inertial measurement unit (GPS/IMU) sensor and the observation sensor such as a hyperspectral sensor, and a lidar sensor. As a result of the physical offset, a misalignment between each image can be occurred along with a flight direction. In particular, in a case of multi-sensor system, an observation sensor has to be replaced regularly to equip another observation sensor, and then, a high cost should be paid to acquire a calibration parameter. In this study, we establish a precise sensor model equation to apply for a multiple sensor in common and propose an independent physical offset estimation method. The proposed method consists of 3 steps. Firstly, we define an appropriate rotation matrix for our system, and an initial sensor model equation for direct-georeferencing. Next, an observation equation for the physical offset estimation is established by extracting a corresponding point between a ground control point and the observed data from a sensor. Finally, the physical offset is estimated based on the observed data, and the precise sensor model equation is established by applying the estimated parameters to the initial sensor model equation. 4 region's datasets(Jeon-ju, Incheon, Alaska, Norway) with a different latitude, longitude were compared to analyze the effects of the calibration parameter. We confirmed that a misalignment between images were adjusted after applying for the physical offset in the sensor model equation. An absolute position accuracy was analyzed in the Incheon dataset, compared to a ground control point. For the hyperspectral image, root mean square error (RMSE) for X, Y direction was calculated for 0.12 m, and for the point cloud, RMSE was calculated for 0.03 m. Furthermore, a relative position accuracy for a specific point between the adjusted point cloud and the hyperspectral images were also analyzed for 0.07 m, so we confirmed that a precise data mapping is available for an observation without a ground control point through the proposed estimation method, and we also confirmed a possibility of multi-sensor fusion. From this study, we expect that a flexible multi-sensor platform system can be operated through the independent parameter estimation method with an economic cost saving.

• Journal of the Korean Association of Geographic Information Studies
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• v.16 no.3
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• pp.103-114
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• 2013

In this study, we established the ortho mosaic imagery on the Korean Peninsula using KOMPSAT-2 images and conducted an accuracy assessment. Rational Polynomial Coefficient(RPC) modeling results were mostly less than 2 pixels except for mountainous regions which was difficult to select a Ground Control Point(GCP). Digital Elevation Model(DEM) which was made using the digital topographic map on the scale of 1:5,000 was used for generating an ortho image. In the case of inaccessible area, the Shuttle Radar Topography Mission(SRTM) DEM was used. Meanwhile, the ortho mosaic image of the Korean Peninsula was produced by each ortho image aggregation and color adjustment. An accuracy analysis for the mosaic image was conducted about a 1m color fusion image. In order to verify a geolocation accuracy, 813 check points which were acquired by field survey in South Korea were used. We found that the maximum error was not to exceed 5m(Root Mean Square Error : RMSE). On the other hand, in the case of inaccessible area, the extracted check points from a reference image were used for accuracy analysis. Approximately 69% of the image has a positional accuracy of less than 3m(RMSE). We found that the seam-line accuracy among neighboring image was very high through visual inspection. However, there were a discrepancy with 1 to 2 pixels at some mountainous regions.