• Title/Summary/Keyword: Error of position

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Simulation Analysis of GPS Reception Environment of Unified Control Points Using GIS (GIS를 이용한 통합기준점의 GPS 수신환경 모의 분석)

  • Kim, Tae Woo;Yun, Hong Sik;Kim, Kwang Bae;Jung, Woon Chul
    • Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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    • v.35 no.6
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    • pp.609-616
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    • 2017
  • National Geographic Information Institute has established a plan that preoccupies UCPs (Unified Control Points) at 2~3km intervals in urban areas by considering the distance between existing UCPs by satellite images and aerial photographs in 2015. In this study, we discussed the method of selecting the locations of optimal UCPs by simulating GPS reception environment in candidate sites for UCPs using GIS. For this purpose, we selected new candidate sites for installing UCPs using satellite images and aerial photographs, and analyzed the GPS reception environment by calculating the visibility distance from buildings around UCPs using GIS skyline analysis. The number of and the arrangement of visible satellites that are capable of GPS satellite reception from the viewpoint of sky view were showed by GIS skyline analysis. Quality evaluation results of GPS observation data were compared with average PDOP calculated from hourly PDOP and TEQC in two points of Sungkyunkwan University during 8 hours. As a result of GPS reception environment using GIS, if the PDOP increases, the data acquisition rate is lowed, and the multipath error and the cycle slip are increased. Thus, this study verified that the quality of GPS observation data can be secured by constructing three-dimensional spatial information and simulating PDOP when preoccupying multiple UCPs using GIS.

Stability Assessment of FKP System by NGII using Long-term Analysis of NTRIP Correction Signal (NTRIP 보정신호 분석을 통한 국토지리정보원 FKP NRTK 시스템 안정성 평가)

  • Kim, Min-Ho;Bae, Tae-Suk
    • Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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    • v.31 no.4
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    • pp.321-329
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    • 2013
  • Despite the advantage of unlimited access, there are insufficient studies for the accuracy and stability of FKP that blocks the spread of the system for various applications. Therefore, we performed a long-term analysis from continuous real-time positioning, and investigated the error characteristics dependent on the size and the surrounding environment. The FKP shows significant changes in the positioning accuracy at different times of day, where the accuracy during daytime is worse than that of nighttime. In addition, the size and deviation of FKP correction may change with the ionospheric conditions, and high correlation between ambiguity resolution rate and the deviation of correction was observed. The receivers continuously request the correction information in order to cope with sudden variability of ionosphere. On the other hand, the correction information was not received up to an hour in case of stable ionospheric condition. It is noteworthy that the outliers of FKP are clustered in their position with some biases. Since several meters of errors can be occurred for kinematic positioning with FKP, therefore, it is necessary to make appropriate preparation for real-time applications.

Analysis of change of internal organ in the Inter-and Intrafraction using MVCT (MVCT를 이용한 치료 간(Interfraction) 그리고 치료 중(Intrafraction) 내부 장기 변화 분석)

  • Jung, Won Seok;Kim, Ju Ho;Kim, Young Jae;Shin, Ryung Mi;Oh, Jeong Hun;Jeong, Geon A;Jo, Jun Young;Kim, Gi Chul;Choi, Tae Kyu
    • The Journal of Korean Society for Radiation Therapy
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    • v.26 no.1
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    • pp.115-126
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    • 2014
  • Purpose : Depending on a variety of therapeutic areas using MVCT(Megavoltage computed tomography) intra-and interfraction is to evaluate changes in patient position. Materials and Methods : In this study, head and neck, thorax, liver, and prostate tumor patients, 48 people with a full course of treatment for patients with various MVCT scan was performed. Average 60 per patient MVCT images were acquired and analyzed. Results : Interfraction error thorax and abdomen, and pelvis in the longitudinal difference was more than 3 mm. Intrafraction to see a change after the end of treatment MVCT taken, and the results confirmed Intrafraction 2 mm in motion around the longitudinal difference. In addition, due to changes in the movement before and after treatment, Inter-and Intrafraction difference was found. Conclusion : In the present study, the Head and Neck, Thorax, liver, prostate cancer in patients with inter-and intrafraction changes and target the appropriate fixtures to complete the outline of the margin would be helpful is considered.

Synthesis and Characterization of the Large Single Crystal of Fully K+-exchanged Zeolite X (FAU), |K80|[Si112Al80O384]-FAU (Si/Al=1.41)

  • Lim, Woo-Taik;Jeong, Gyo-Cheol;Park, Chang-Kun;Park, Jong-Sam;Kim, Young-Hun
    • Bulletin of the Korean Chemical Society
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    • v.28 no.1
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    • pp.41-48
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    • 2007
  • Large colorless single crystals of sodium zeolite X, stoichiometry |Na80 |[Si112Al80O384]-FAU, with diameters up to 200 μm and Si/Al = 1.41 have been synthesized from gels with the composition of 2.40SiO2 : 2.00NaAlO2 : 7.52NaOH : 454H2O : 5.00TEA. One of these, a colorless octahedron about 200 μm in cross-section has been treated with aqueous 0.1 M KNO3 for the preparation of K+-exchanged zeolite X. The crystal structure of |K80|[Si112Al80O384]-FAU per unit cell, a = 24.838(4) A, dehydrated at 673 K and 1 × 10-6 Torr, has been determined by single-crystal X-ray diffraction techniques in the cubic space group Fd at 294 K. The structure was refined using all intensities to the final error indices (using only the 707 reflections for which Fo > 4σ (Fo)) R1 = 0.075 (based on F) and R2 = 0.236 (based on F2). About 80 K+ ions per unit cell are found at an unusually large number of crystallographically distinct positions, eight. Eleven K+ ions are at the centers of double 6-rings (D6Rs, site I; K-O = 2.492(6) A and O-K-O (octahedral) = 88.45(22)o and 91.55(22)o). Site-I' position (in the sodalite cavities opposite D6Rs) is occupied by five K+ ions per unit cell; these K+ ions are recessed 1.92 A into the sodalite cavities from their 3-oxygen planes (K-O = 2.820(19) A, and O-K-O = 78.6(6)o). Twety-three K+ ions are found at three nonequivalent site II (in the supercage) with occupancies of 5, 9, and 9 ions; these K+ ions are recessed 0.43 A, 0.75 A, and 1.55 A, respectively, into the supercage from the three oxygens to which it is bound (K-O = 2.36(13) A, 2.45(13) A, and 2.710(13) A, O-K-O = 116.5(20)o, 110.1(17)o, and 90.4(6)o, respectively). The remaining sixteen, thirteen, and twelve K+ ions occupy three sites III' near triple 4-rings in the supercage (K-O = 2.64(3) A, 2.94(3) A, 2.73(5) A, 2.96(6) A, 3.06(4) A, and 3.08(3) A).

Imputation of Missing SST Observation Data Using Multivariate Bidirectional RNN (다변수 Bidirectional RNN을 이용한 표층수온 결측 데이터 보간)

  • Shin, YongTak;Kim, Dong-Hoon;Kim, Hyeon-Jae;Lim, Chaewook;Woo, Seung-Buhm
    • Journal of Korean Society of Coastal and Ocean Engineers
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    • v.34 no.4
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    • pp.109-118
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    • 2022
  • The data of the missing section among the vertex surface sea temperature observation data was imputed using the Bidirectional Recurrent Neural Network(BiRNN). Among artificial intelligence techniques, Recurrent Neural Networks (RNNs), which are commonly used for time series data, only estimate in the direction of time flow or in the reverse direction to the missing estimation position, so the estimation performance is poor in the long-term missing section. On the other hand, in this study, estimation performance can be improved even for long-term missing data by estimating in both directions before and after the missing section. Also, by using all available data around the observation point (sea surface temperature, temperature, wind field, atmospheric pressure, humidity), the imputation performance was further improved by estimating the imputation data from these correlations together. For performance verification, a statistical model, Multivariate Imputation by Chained Equations (MICE), a machine learning-based Random Forest model, and an RNN model using Long Short-Term Memory (LSTM) were compared. For imputation of long-term missing for 7 days, the average accuracy of the BiRNN/statistical models is 70.8%/61.2%, respectively, and the average error is 0.28 degrees/0.44 degrees, respectively, so the BiRNN model performs better than other models. By applying a temporal decay factor representing the missing pattern, it is judged that the BiRNN technique has better imputation performance than the existing method as the missing section becomes longer.

A Study on Development of Technology System for Deep-Sea Unmanned Underwater Robot of S. Korea analysed by the Application of Scenario Planning (한국형 수중로봇시스템의 기술개발연구 - 시나리오플래닝 적용으로 -)

  • Lee, Sang-Yun;Yoon, Hong-Joo
    • The Journal of the Korea institute of electronic communication sciences
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    • v.8 no.1
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    • pp.27-40
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    • 2013
  • This study is about development of technology system for an advanced deep-sea unmanned underwater robot of S. Korea analysed by the application of scenario planning. It was developed a 6000m class next-generation deep-sea unmanned underwater vehicle(or robot, UUV) system, soonly ROV 'Hemire' and Depressor 'Henuvy' in 2006 at S. Korea and motion control, adaptive control algolithm, a work-space manipulator control algolithm, especially the underwater inertial-acoustic navigation system robust to initial errors and sensor failures. But there are remained matters on position tracking of the USBL, inertial-acoustic navigation system, attitude sensor, designed sonar sensors. So this study suggest the new idea for settle the matters and then this idea help the development of the underwater inertial-acoustic navigation system robust to initial errors and sensor failures, such as acoustic signal drop-out, by modifying the error covariance of the failed sonar signal when drop-out occurs. As a result, the future policy for deep-sea unmanned underwater robot of S. Korea is to further spur the development of new technology and more improvement of the technology level for deep-sea unmanned underwater robot system with indicator and imaginary wall as external device.

A study on vision system based on Generalized Hough Transform 2-D object recognition (Generalized Hough Transform을 이용한 이차원 물체인식 비젼 시스템 구현에 대한 연구)

  • Koo, Bon-Cheol;Park, Jin-Soo;Chien Sung-Il
    • Journal of the Korean Institute of Telematics and Electronics B
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    • v.33B no.1
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    • pp.67-78
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    • 1996
  • The purpose of this paper is object recognition even in the presence of occlusion by using generalized Hough transform(GHT). The GHT can be considered as a kind of model based object recognition algorithm and is executed in the following two stages. The first stage is to store the information of the model in the form of R-table (Reference table). The next stage is to identify the existence of the objects in the image by using the R-table. The improved GHT method is proposed for the practical vision system. First, in constructing the R-table, we extracted the partial arc from the portion of the whole object boundary, and this partial arc can be used for constructing the R-table. Also, clustering algorithm is employed for compensating an error arised by digitizing an object image. Second, an efficient method is introduced to avoid Ballard's use of 4-D array which is necessary for estimating position, orientation and scale change of an object. Only 2-D array is enough for recognizing an object. Especially, scale token method is introduced for calculating the scale change which is easily affected by camera zoom. The results of our test show that the improved hierarchical GHT method operates stably in the realistic vision situation, even in the case of object occlusion.

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Accuracy of Parcel Boundary Demarcation in Agricultural Area Using UAV-Photogrammetry (무인 항공사진측량에 의한 농경지 필지 경계설정 정확도)

  • Sung, Sang Min;Lee, Jae One
    • Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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    • v.34 no.1
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    • pp.53-62
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    • 2016
  • In recent years, UAV Photogrammetry based on an ultra-light UAS(Unmanned Aerial System) installed with a low-cost compact navigation device and a camera has attracted great attention through fast and accurate acquirement of geo-spatial data. In particular, UAV Photogrammetry do gradually replace the traditional aerial photogrammetry because it is able to produce DEMs(Digital Elevation Models) and Orthophotos rapidly owing to large amounts of high resolution image collection by a low-cost camera and image processing software combined with computer vision technique. With these advantages, UAV-Photogrammetry has therefore been applying to a large scale mapping and cadastral surveying that require accurate position information. This paper presents experimental results of an accuracy performance test with images of 4cm GSD from a fixed wing UAS to demarcate parcel boundaries in agricultural area. Consequently, the accuracy of boundary point extracted from UAS orthoimage has shown less than 8cm compared with that of terrestrial cadastral surveying. This means that UAV images satisfy the tolerance limit of distance error in cadastral surveying for the scale of 1: 500. And also, the area deviation is negligible small, about 0.2%(3.3m2), against true area of 1,969m2 by cadastral surveying. UAV-Photogrammetry is therefore as a promising technology to demarcate parcel boundaries.

VLC Based Positioning Scheme in Vehicle-to-Infra(V2I) Environment (차량-인프라간 가시광 통신 기반 측위 기술)

  • Kim, Byung Wook;Song, Deok-Weon;Lee, Ji-Hwan;Jung, Sung-Yoon
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.40 no.3
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    • pp.588-594
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    • 2015
  • Although GPS technology for location positioning system has been widely used, it is difficult to be used in intelligent transport systems, due to the large positioning error and limited area for receiving radio signals. Thanks to the rapid development of LED technology, LED lights become popular in many applications. Especially, visible light communications (VLC) has raised a lot of interests because of the simultaneous functioning of LED illumination and communication. Recent studies on positioning system using VLC mainly focused on indoor environments and still difficult to satisfy positioning accuracy and simple implementation simultaneously. In this paper, we propose a positioning system based on VLC using the coordinate information of LEDs installed on the road infrastructure. Extracting the LED signal, obtained through VLC, from the easily accessible camera image, it is possible to estimate the position of the car on the road. Simulation results show that the proposed scheme can achieve a high positioning accuracy of 1 m when large number of pixels is utilized and the distance from the LED light is close.

Sliding Mode Control with Super-Twisting Algorithm for Surge Oscillation of Mooring Vessel System (슈퍼트위스팅 슬라이딩모드를 이용한 선박계류시스템의 동적제어)

  • Lee, Sang-Do;Lee, Bo-Kyeong;You, Sam-Sang
    • Journal of the Korean Society of Marine Environment & Safety
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    • v.24 no.7
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    • pp.953-959
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    • 2018
  • This paper deals with controlling surge oscillations of a mooring vessel system under large external disturbances such as wind, waves and currents. A control synthesis based on Sliding Mode Control (SMC) with a Super-Twisting Algorithm (STA) has been applied to suppress nonlinear surge oscillations of a two-point mooring system. Despite the advantages of robustness against parameter uncertainties and disturbances for SMC, chattering is the main drawback for implementing sliding mode controllers. First-order SMC shows convergence within the desired level of accuracy, in which chattering is the main obstacle related to the destructive phenomenon. Alternatively, STA completely eliminates chattering phenomenon with high accuracy even for large disturbances. SMC based on STA is an effective tool for the motion control of a nonlinear mooring system because it avoids the chattering problems of a first-order sliding mode controller. In addition, the error trajectories of controlled mooring systems implemented by means of STA form in the bounded region. Finally, the control gain effect of STA can be observed in sliding surface and position trajectory errors.