• 제목/요약/키워드: Urban Canyon

검색결과 53건 처리시간 0.02초

Analysis of the effect of street green structure on PM2.5 in the walk space - Using microclimate simulation - (가로녹지 유형이 보행공간의 초미세먼지에 미치는 영향 분석 - 미기후 시뮬레이션을 활용하여 -)

  • Kim, Shin-Woo;Lee, Dong-Kun;Bae, Chae-Young
    • Journal of the Korean Society of Environmental Restoration Technology
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    • 제24권4호
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    • pp.61-75
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    • 2021
  • Roadside greenery in the city is not only a means of reducing fine dust, but also an indispensable element of the city in various aspects such as improvement of urban thermal environment, noise reduction, ecosystem connectivity, and aesthetics. However, in studies dealing with the effect of reducing fine dust through trees in existing urban spaces, microscopic aspects such as the adsorption effect of plants were dealt with, structural changes such as the width of urban buildings and streets, and the presence or absence of trees, Impact studies that reflect the actual form of In this study, the effect of greenery composition applicable to urban space on PM2.5 was simulated through the microclimate epidemiologic model ENVI-met, and field measurements were performed in parallel to verify the results. In addition, by analyzing the results of fine dust background concentration, wind speed, and leaf area index, the sensitivity to major influencing variables was tested. As a result of the study, it was confirmed that the fine dust reduction effect was the highest in the case with a high planting amount, and the reduction effect was the greatest at a low background concentration. Based on this, the cost of planting street green areas and the effect of reducing PM2.5 were compared. The results of this study can contribute as a basis for considering the effect of pedestrian space on air quality when planning and designing street green spaces.

Study on Detailed Air Flows in Urban Areas Using GIS Data in a Vector Format and a CFD Model (벡터 형식의 GIS 자료와 CFD 모델을 이용한 도시 지역 상세 대기 흐름 연구)

  • Kwon, A-Rum;Kim, Jae-Jin
    • Korean Journal of Remote Sensing
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    • 제30권6호
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    • pp.755-767
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    • 2014
  • In this study, detailed air flow characteristics in an urban areas were analyzed using GIS data and a Computational Fluid Dynamics (CFD) model. For this, a building construction algorithm optimized for Geographic Information System (GIS) data with a vector format (Los Angeles region imagery acquisition consortium 2 geographic information system, LARIAC2 GIS) was used. In the LARIAC2 GIS data, building vertices were expressed as latitude and longitude. Using the model buildings constructed by the algorithm as the surface boundary data in the CFD model, we performed numerical simulations for two building-congested areas in Los Angeles using inflow information provided by California Air Resources Board. Comparing with the inflow, there was a marked difference in wind speed and direction within the target areas, which was mainly caused by the secondarily induced local circulations such as street-canyon vortices, horse-shoe vortices, and recirculation zones. In street canyons parallel to the inflow direction, wind speed increased due to a channeling effect and, in street canyons perpendicular to the inflow direction, vertically well developed vortices were induced. In front of a building, a horse-shoe vortex was developed near the surface and, behind a building, a recirculation zone was developed. Near the surface in the areas where the secondarily induced local circulations, wind speed remarkably increased. Overall, wind direction little (largely) changed at the areas where wind speed largely increased (decreased).

Analysis of 3D GIS- Based GNSS Visibility at Urban Area (도심에서의 3차원 GIS 기반 위성항법시스템 가시성 분석)

  • Yoo, Kyung-Ho;Kang, Tae-Sam;Sung, Sang-Kyung;Lee, Eun-Sung;Jeong, Seong-Kyun;Sin, Cheon-Sig;Lee, Sang-Uk;Lee, Young-Jae
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • 제35권12호
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    • pp.1095-1100
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    • 2007
  • Visibility of the satellite navigation is related to a environmental condition of a receiver. Obstacles like buildings and trees in urban areas can block signals and have effects on accuracy and reliability of positioning. This paper presents a method of creating 3D analysis model of urban canyon of Seoul using three-Dimensional digital map. Analysis techniques of visible satellites with Ray-Polygon Collision Detection and validation of algorithm through field tests are discussed. We have compared and analyzed the visibility of GPS and Galileo with respect to separate and simultaneous tracking in view of DOP (Dilution of Precision) using the 3D GIS digital map.

Assisted GNSS Positioning for Urban Navigation Based on Receiver Clock Bias Estimation and Prediction Using Improved ARMA Model

  • Xia, Linyuan;Mok, Esmond
    • Proceedings of the Korean Institute of Navigation and Port Research Conference
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    • 한국항해항만학회 2006년도 International Symposium on GPS/GNSS Vol.1
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    • pp.395-400
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    • 2006
  • Among the various error sources in positioning and navigation, the paper focuses on the modeling and prediction of receiver clock bias and then tries to achieve positioning based on simulated and predicted clock bias. With the SA off, it is possible to model receiver clock bias more accurately. We selected several types of GNSS receivers for test using ARMA model. To facilitate prediction with short and limited sample pseudorange observations, AR and ARMA are compared, and the improved AR model is presented to model and predict receiver clock bias based on previous solutions. Our work extends to clock bias prediction and positioning based on predicted clock bias using only 3 satellites that is usually the case under urban canyon situation. In contrast to previous experiences, we find that a receiver clock bias can be well modeled using adopted ARMA model. Test has been done on various types of GNSS receivers to show the validation of developed model. To further develop this work, we compare solution conditions in terms of DOP values when point positioning is conducted using 3 satellites to simulate urban positioning environment. When condition allows, height component is derived from other ways and can be set as known values. Given this condition, location is possible using less than 2 GNSS satellites with fixed height. Solution condition is also discussed for this background using mode of constrained positioning. We finally suggest an effective predictive time span based on our test exploration under varied conditions.

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Accuracy Estimation of Car Navigation using GPS CORS (GPS 상시관측점을 이용한 차량항법 정확도 평가)

  • 박운용;김희규;이재원;신상철
    • Proceedings of the Korean Society of Surveying, Geodesy, Photogrammetry, and Cartography Conference
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    • 한국측량학회 2004년도 춘계학술발표회논문집
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    • pp.103-106
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    • 2004
  • Nowadays it is necessary to manage the road system effectively because of the explosive increment of vehicle and goods. To resolve this problems through the fast upgrade of information about position and time of moving vehicle, the combined navigation system using GPS and complementary navigation system, i.e. INS, DR, etc. has been used. Although GPS is popular for the vehicle navigation system, this is not useful for the kinematic positioning of the vehicles in the urban canyon because of its few satellites. Therefore, this study deals with the kinematic positioning of the vehicles with GPS CORS to GPS navigation. For this, first the static single point positioning of GPS and GPS for reference station was performed to evaluate the accuracy of GPS positioning. Next, in the post-processed, the DGPS (Differential GPS) was performed for the kinematic positioning of the vehicles. So, it is expected that GPS CORS can be applicable to the control of traffic flow, the effective management of road system, and the development of ITS and it is regarded that the combined navigation system of vehicles with GPS, INS, and DR, etc. should be studied constantly.

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Kinematic Positioning of Vehicle with Real-time DGPS/DGLONASS (Real-time DGPS/DGLONASS에 의한 차량의 동적위치결정에 관한 연구)

  • 박운용;이인수;신상철;곽재하
    • Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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    • 제19권3호
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    • pp.301-308
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    • 2001
  • Nowadays GPS play a important roles in the navigation system of vehicles, but, it doesn't determine the kinematic positions of vehicles accurately because of few satellites in the urban canyon covered with trees and high buildings. So GLONASS (GLObal Navigation Satellites System), the Russian satellites'system, operated in 1996, was introduced to overcome this drawbacks. Therefore, this study deals with the kinematic positioning of vehicles with Real-time code differential positioning methods. As a result, Real-time DGPS/GLONASS is better than Real-time DGPS in the differential corrected positions and HDOP (Horizontal Dilution of Precision). And it was shown that the combined GPS/GLONASS contributes to the precise kinematic positioning of vehicles.

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New TDOA-Based Three-Dimensional Positioning Method for 3GPP LTE System

  • Lee, Kyunghoon;Hwang, Wonjun;Ryu, Hyunseok;Choi, Hyung-Jin
    • ETRI Journal
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    • 제39권2호
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    • pp.264-274
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    • 2017
  • Recently, mobile positioning enhancement has attracted much attention in the 3rd generation partnership project long-term evolution system. In particular, for urban canyon environments, the need for three-dimensional (3D) positioning has increased to enable the altitude of users to be measured. For several decades, several time difference of arrival (TDOA-) based 3D positioning methods have been studied; however, they are only available when at least four evolved Node Bs (eNBs) exist nearby or when all eNBs have the same height. Therefore, in this paper, we propose a new 3D positioning method that estimates the 3D coordinates of a user using three types of two-dimensional (2D) TDOAs. However, the give inaccurate results owing to the undefined axis of the 2D coordinate plane. Therefore, we propose a novel derivation of the hyperbola equation, which includes the undefined axis coordinate in the 2D hyperbola equation. Then, we propose an interaction algorithm that mutually supplies the undefined axis coordinate of users among 2D TDOAs. By performing extensive simulations, we verify that the proposed method is the only solution applicable by using three eNBs with different heights.

Analysis of Factors Affecting Performance of Integrated INS/SPR Positioning during GPS Signal Blockage

  • Kang, Beom Yeon;Han, Joong-hee;Kwon, Jay Hyoun
    • Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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    • 제32권6호
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    • pp.599-606
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    • 2014
  • Since the accuracy of Global Positioning System (GPS)-based vehicle positioning system is significantly degraded or does not work appropriately in the urban canyon, the integration techniques of GPS with Inertial Navigation System (INS) have intensively been developed to improve the continuity and reliability of positioning. However, its accuracy is degraded as INS errors are not properly corrected due to the GPS signal blockage. Recently, the image-based positioning techniques have been started to apply for the vehicle positioning for the advanced in processing techniques as well as the increased the number of cars installing the camera. In this study, Single Photo Resection (SPR), which calculates the camera exterior orientation parameters using the Ground Control Points (GCPs,) has been integrated with the INS/GPS for continuous and stable positioning. The INS/GPS/SPR integration was implemented in both of a loosely and a tightly coupled modes, based on the Extended Kalman Filter (EKF). In order to analyze the performance of INS/SPR integration during the GPS outage, the simulation tests were conducted with a consideration of factors affecting SPR performance. The results demonstrate that the accuracy of INS/SPR integration is depended on magnitudes of the GCP errors and SPR processing intervals. Additionally, the simulation results suggest some required conditions to achieve accurate and continuous positioning, used the INS/SPR integration.

The Technical Benefits of Future GNSS for Taiwan

  • Chiang, Kai-Wei;Yang, Ming;Tsai, Meng-Lun;Chang, Yao-Yun;Chu, Chi-Kuang
    • Proceedings of the Korean Institute of Navigation and Port Research Conference
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    • 한국항해항만학회 2006년도 International Symposium on GPS/GNSS Vol.2
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    • pp.3-8
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    • 2006
  • The next decade promises drastic improvements and additions to global navigation satellite systems (GNSS). Plans for GPS modernization include a civilian code measurement on the L2 frequency and a new L5 signal at 1176.45 MHz. Current speculations indicate that a fully operational constellation with these improvements could be available by 2013. Simultaneously, the Galileo Joint Undertaking is in the development and validation stages of introducing a parallel GNSS called Galileo. Galileo will also transmit freely available satellite navigation signals on three frequencies and is scheduled to be fully operational as early as 2008. In other words, a dual system receiver (e.g., GPS+GALILEO) for general users can access six civil frequencies transmitted by at least fifty eights navigation satellites in space. The advent of GALILEO and the modernization of GPS raise a lot of attention to the study of the compatibility and interoperability of the two systems. A number of performance analyses have been conducted in a global scale with respect to availability, reliability, accuracy and integrity in different simulated scenarios (such as open sky and urban canyons) for the two systems individually and when integrated. Therefore, the scope of this article aims at providing the technical benefits analysis for Taiwan specifically in terms of the performance indices mentioned above in a local scale, especially in typical urban canyon scenarios. The conclusions gained by this study will be applied by the Land Survey Bureau of Taiwanese as the guideline for developing future GNSS tracking facilities and dual GNSS processing module for precise surveying applications in static and kinematic modes.

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Navigation Augmentation in Urban Area by HALE UAV with Onboard Pseudolite during Multi-Purpose Missions

  • Kim, O-Jong;Yu, Sunkyoung;No, Heekwon;Kee, Changdon;Choi, Minwoo;Seok, Hyojeong;Yoon, Donghwan;Park, Byungwoon;Jee, Cheolkyu
    • International Journal of Aeronautical and Space Sciences
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    • 제18권3호
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    • pp.545-554
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    • 2017
  • Among various applications of the High Altitude Long Endurance (HALE) Unmanned Aerial Vehicle (UAV), this paper has a focus on the Global Positioning System (GPS) utilizing pseudolite and its improved performance, particularly during the multi-purpose missions. In a multi-purpose mission, the HALE UAV follows a specified flight trajectory for both navigation applications and missions. Some of the representative HALE missions are remote exploration, surveillance, reconnaissance, and communication relay. During these operations, the HALE UAV can also be an additional positioning signal source as it broadcast signals using pseudolite. The pseudolite signal can improve the availability, accuracy, and reliability of the GPS particularly in areas with poor signal reception, such as shadowed regions between tall buildings. The improvement in performance of navigation is validated through simulations of multi-purpose missions of the solar-powered HALE UAV in an urban canyon. The simulation includes UAV trajectory generation at stratosphere and uses actual geographical building data. The results indicate that the pseudolite-equipped HALE UAV has the potential to enhance the performance of the satellite navigation system in navigationally degraded regions even during multi-purpose operations.