• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.19 no.11
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• pp.1126-1132
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• 2009

Bridge structures are designed to support ordinary loadings such as vehicles, wind, temperature and current as well as unexpected loadings like earthquakes and storm. Especially, the displacement of Flexible bridges like an suspension bridge under ordinary loading conditions is necessary to be monitored. In case of long span bridges, there are some difficulties in monitoring the displacement of center of the main span using traditional laser displacement sensors. In this study, the static and dynamic displacement responses due to vehicle loadings were measured by DGPS(differential global positioning system) technique. The displacement response data were compared with data obtained from traditional laser displacement sensors so that the static and dynamic behavior of the bridge under vehicle loadings was examined and the applicability of the displacement response measurement using DGPS technique was verified. The static and dynamic loading test for an self-anchored suspension bridge, So-rok Bridge, was performed using vehicles. The displacement response from DGPS technique and that from laser displacement sensors of the bridge monitoring system were compared. The amplitude of white noise from DGPS based measurement was about 7 mm and that of laser displacement sensor based measurement was about 3 mm. On the other hand, dynamic behavior of the center of main span from DGPS based measurement showed better agreement with influence line of the bridge than that from laser displacement sensors. In addition, there were some irregular and discontinuous variation of data due to the instability of GPS receivers or frequent appearance of GPS satellites. Post-processing via the reference station close to an observation post provided by NGII(National Geographic Information Institute) will be a counter-plan for these defects.

• International Journal of Aeronautical and Space Sciences
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• v.6 no.1
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• pp.44-51
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• 2005

To provide more accurate and reliable positioning and timing services to Korean nationwide users, the Ministry of Maritime Affairs and Fisheries of Korea is implementing Korean NDGPS (Nationwide DGPS), which is operational partly. And it also has a plan to construct WADGPS (Wide Area Differential GPS) system using sites and equipments of the NDGPS reference stations. For that, Seoul National University GNSS Laboratory is implementing and testing prototypes of WRS (Wide-area Reference Station) and WMS (Wide-area Master Station). Until now, because there are not enough installed WRSs to be used for computing wide area correction information, we cannot test algorithms of WMS with the data processed actually in WRSs. Therefore to evaluate the performance of the algorithms, we made a MATLAB program which can process RINEX (Receiver INdependent Exchange) format data with WADGPS algorithm. Using that program which consists of WRS, WMS and USER modules, we processed the data collected at NDGPS reference stations, which are saved in RINEX format. In WRS module, we eliminate the atmospheric delay error from the pseudorange measurement, smooth the measurement by hatch filter and calculate pseudorange corrections for each satellite. WMS module collects the processed data from each reference stations to generate the wide area correction information including estimated satellite ephemeris errors, ionospheric delays at each grid point, UDRE (User Differential Range Error), GIVE (Grid Ionosphere Vertical Error) and so on. In USER part, we use the measurements of reference stations as those of users and estimate the corrected users' positions and protection levels (HPL, VPL). With the results of estimation, we analyzed the performance of the algorithms. We assured the estimated UDRE /GIVE values and the protection levels bound the corresponding errors effectively. In this research, we can expect the possible performance of WADGPS in Korea, and the developed modules will be useful to implementation and improvement of the algorithms.

• Spatial Information Research
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• v.7 no.2
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• pp.209-221
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• 1999

In this research, AVL-GIS(Automatic Vehicle Location System linked with Geographic Information System) system was developed using integration of core techniques of GIS engine written by Java language, GOS(Global Positioning System) and wireless telecommunication interfacing techniques. IDGPS(Inverted differential GPS) techniques was employed to estimate accurate position of mobile vehicle and to supervise their path from AVL-GLS control center system. Between mobile vehicle and AVL-GLS control center system which has spatial data analysis function, road network and rleate ddata base were connected wireless phone to communicate for position an dmessage in real time. The developed system from this research has more enhanced GIS functions rather than previous AVL oriented system which has MDT for message display and voice communication only. This system can support build-up application system such as fleet management like bus, taxi, truck, disaster and emergency and monitoring of transportation status for customer s order via web browser in filed of EC/CALS in low cost.

• Journal of Advanced Navigation Technology
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• v.22 no.5
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• pp.400-408
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• 2018

Wide area augmentation system is a system that generates and transmits correction and Integrity information for use in wide area. Typical system is SBAS. In the United States, it operates under the name WAAS, EGNOS in Europe, MSAS in Japan, SDCM in Russia, GAGAN in India. it is developing Korean SBAS which named KASS by 2022 in Korea. SBAS is a standard System that is operated as civil aviation service base and set as international standards by ICAO. So the correction data can only is used for civil SPS receiver. In this paper, we discuss C1P1 DCB estimation which need to use SPS correction service for PPS receiver. Then we analyze C1P1 DCB correction effect under standalone Satellite Navigation and method to use PPS receiver under SPS DGPS. Finally we organize wide area augmentation system for PPS receiver and analysis performance.

• Journal of Institute of Control, Robotics and Systems
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• v.17 no.7
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• pp.674-684
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• 2011

More and more elderly and disabled people are using electric scooters instead of electric wheelchairs because of higher mobility. However, people with high levels of impairment or the elderly still have difficulties in driving the electric scooters safely. Semi-autonomous electric scooter system is one of the solutions for the safety: Either manual driving or autonomous driving can be used selectively. In this paper, we implement a semi-autonomous electric scooter system with functions of localization and path following. In order to recognize the pose of electric scooter in outdoor environments, we design an outdoor localization system based on the extended Kalman filter using DGPS (Differential Global Positioning System) and wheel encoders. We added an accelerometer to make the localization system adaptable to road condition. Also we propose a path following algorithm using two arcs with current pose of the electric scooter and a given path in the map. Simulation results are described to show that the proposed algorithms provide the ability to drive an electric scooter semi-autonomously. Finally, we conduct outdoor experiments to reveal the practicality of the proposed system.

• IEIE Transactions on Smart Processing and Computing
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• v.2 no.2
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• pp.45-56
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• 2013

The precise identification of vehicle positions, known as the vehicle localization problem, is an important requirement for building intelligent vehicle ad-hoc networks (VANETs). To solve this problem, two categories of solutions are proposed: stand-alone and data fusion approaches. Compared to stand-alone approaches, which use single information including the global positioning system (GPS) and sensor-based navigation systems with differential corrections, data fusion approaches analyze the position information of several vehicles from GPS and sensor-based navigation systems, etc. Therefore, data fusion approaches show high accuracy. With the position information on a set of vehicles in the preprocessing stage, data fusion approaches is used to estimate the precise vehicular location in the local map building stage. This paper proposes an efficient local map building scheme, which increases the accuracy of the estimated vehicle positions via V2V communications. Even under the low ratio of vehicles with communication modules on the road, the proposed local map building scheme showed high accuracy when estimating the vehicle positions. From the experimental results based on the parameters of the practical vehicular environments, the accuracy of the proposed localization system approached the single lane-level.

• Journal of the Korean Society of Clothing and Textiles
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• v.24 no.6
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• pp.861-872
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• 2000

The purpose of this study is to objectively explain the visual sensibility of clothing pattern and develop the design of clothing pattern that satisfies the consumer's sensibility. The photos stimuli on clothing pattern are divided into source, presentation, layout and are composed of each 6 photos per chapter totally 48 photos and semantic differential bi-polar scales are consist of 27 couples sensibility words. The subjects were 400 females in the twenties. Data were analyzed by SAS. The major finds were as follows: 1. As a result of the factor analysis, 4 factors of visual sensibility were consist of Coordination, Hardness and Softness, Attention, Rhythm. 2. As to the difference of visual sensibility based on the composition of clothing pattern, there were differences Hardness and Softness, Rhythm by source and there were significant differences among 4 factors by presentation and layout. 3. According to the age and education level, there were significant differences in Attention, Rhythm and according to the consuming areas, there were significant differences in Coordination, Rhythm. 4. According to sensibility positioning, The clothing pattern was classified as soft-hard, simple-complicated. 5. As a result of the regression analysis, preference, consuming desire and satisfaction appears to be closely related. Good quality is related with total clothing image which is brought about composition of clothing pattern.

• Bulletin of the Korean Space Science Society
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• 2011.04a
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• pp.25.5-26
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• 2011

이 연구에서는 네트워크 기반의 다중기준국을 이용하여 육상교통환경에서 항법위성의 궤도력에 따른 위치결정 성능향상의 정도를 분석하였다. 위성항법보정시스템(Differential Global Positioning System)을 활용하였을 경우 항법위성의 궤도력 오차정보가 소거되지 않는다는 가정 하에 방송궤도력이 아닌 International GNSS Service(IGS) 정밀궤도력중 신속궤도력(Ultra-Rapid)을 이용하여 궤도력 오차에 따라 위치결정 정확도가 향상됨을 확인하였다. 일반적으로 사용하는 위성항법보정시스템을 활용한 위치결정 방법은 기준국과 사용자의 거리에 따라서 그 성능이 달라진다. 이는 궤도 오차, 대류층 및 전리층 오차 등이 거리에 의존적이기 때문이다. 다중기준국을 활용하는 방법은 거리가 멀어짐에 따라 소거되지 않는 오차등을 극복하기 위한 기술이며 사용자 주변을 둘러싼 기준국들의 측정값을 조합하여 보상을 하거나 정확하게 모델링하여 사용자에게 오차정보를 보정정보로 전송하여 위치결정의 성능을 향상시키는 방법이다. 분석된 결과는 네트워크 기반의 다중기준국 환경에서 사용자와 기준국간의 거리에 따른 공간이격 오차정보 보정정보 생성 연구에 활용하며 이를 통해 육상교통 사용자의 위치결정 정확도 성능을 향상하는데 기여할 것으로 기대된다.

• Journal of the Korea Institute of Military Science and Technology
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• v.14 no.5
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• pp.788-797
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• 2011

This paper analyzes the accuracy on the approach and landing of aircraft to an airport through comparison with airbase Precision Approach Radar and aircraft track data of DGPS equipped in aircraft. The proposed analysis result could be a basis for verifying the possibility that DGPS can be utilized in Airbase precision approach and landing. Position identification capability of widely used commercial DGPS is fairly accurate on latitude and longitude, while there is a slight error for being used in an airbase accurate approach and landing of Category I precision when it comes to altitude. Thus, we tested accuracy by analyzing actual flight track data of high performance aircraft to verify the accuracy of the airbase approach and landing using DGPS. Through the research, we developed instrumentation to compare PAR track data with DGPS track data, which can be used in reducing the number of PAR verification Flight utilizing it as a system measuring PAR accuracy at PAR installation phase.

• Journal of the Korean Institute of Navigation
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• v.24 no.5
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• pp.405-415
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• 2000

DGPS/Radio beacons are currently being planned or installed in many countries. They offer a cost-effective way of distributing differential data to large number of users. These networks are also being deployed in South Korea, Japan, and China. Several DGPS stations among them are operating on the same frequencies. The DGPS signal based on a radio beacon in medium frequency band travels principally as a groundwave over the surface of the earth. The signal may also be received as skywaves at locations beyond about 100 km from the reference station. These skywaves interfere with groundwave signals due to fading. This factor has generally ignored in designing DGPS/Radio beacon systems. A further important factor is to reduce the coverage due to interference from other beacons on the same or adjacent frequencies. The desired signal may fade due to interaction between its skywave and groundwave components. It may degrade the accuracy of the positioning in a complex fashion. This paper estimates the coverage of Far East Asia DGPS stations which are operating on the same frequencies, which is based on the signal protection ratio and interference of the signal strength of the groundwave and skywave.