• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.11 no.5
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• pp.62-69
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• 2012

Traffic simulation models have been used for assessing various transportation strategies. Through comparing results from a simulation model and real field data, researchers try to show how close the model can reproduce the real world traffic. This model verification step is one of the most essential tasks in modeling procedure. Traffic counts and speeds have been frequently used for the verification or validation. Authors modeled severe PM peak bottleneck situation on the I-40 corridor in Raleigh, North Carolina using DYNASMART-P, a mesoscopic traffic simulation tool and verified the model. NCDOT has Traffic Information Management System which has archive capability for the traffic speeds on the I-40 corridor. However, the authors selected travel time as the field measure for model verification and collected the data using a GPS equipment because the speed data from NCDOT speed detectors are spot speeds which are not appropriate for comparison with link average speed from the simulation model. This paper describes the GPS field data collection procedure, the model verification method, and the results.

• Korean Journal of Construction Engineering and Management
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• v.13 no.3
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• pp.56-66
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• 2012

The Recent Specialty Contractor in construction of the reduced quantity due to the recession, but competitive in order to increase the number of companies that are increasingly competitive. The field work of one person to perform the work of employees and multiple sites, workforce supply flow that occurs at each stage of information transfer is not made a late staffing. Therefore this research has proposed a new alternative that can overcome them and the entire industry in recent issue smart phone features that take advantage of GPS(Global Positioning System). This paper presents a Diligence and Indolence Management System using GPS of smart phone. offering the advantage of Web-based PMIS(Project Management Information System) through integration with real-time information transfer and smart phone applications for query by building a prototype of a professional construction company as their own on-site management measures are proposed to contribute time and attendance.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.26 no.2
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• pp.139-147
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• 2008

The positioning accuracies tend to deteriorate as the distance between the rover and the reference station increases in the Real-Time Kinematic (RTK) surveys using Global Positioning System (GPS). To solve this problem, the National Geographic Information Institute (NGII) of Korea has installed Virtual Reference System (VRS), which is one of the network-based RTK systems. In this study, we conducted the accuracy tests of the VRS-RTK surveys. We surveyed 50 control points inside the NGII's GPS Continuously Operating Reference Stations (CORS) network using the VRS-RTK system, and compared the results with the published coordinates to verify the positioning accuracies. We also conducted the general RTK surveys at the same control points. The results showed that the positioning accuracy of the VRS-RTK was comparable to that of the general RTK, because the horizontal positioning accuracy was 3.1 cm while that of general RTK was 2.0 cm. Also the vertical positioning accuracy of VRS-RTK was 6.8 cm.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.26 no.5
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• pp.493-504
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• 2008

Space-Based Augmentation System (SBAS), which is one of the GPS augmentation systems, is a Wide-Area Differential GPS that provides differential GPS corrections and integrity data. In this study, we did performance analysis of kinematic SBAS surveying by conducting Real-Time Kinematic (RTK), DGPS, standalone, and SBAS surveys. Considering static survey results as truth, 2-D Root Mean Square (RMS) error and 3-D RMS error were computed to evaluate the positioning accuracy of each survey method. As a result, the 3-D positioning error of RTK was 13.1cm, DGPS 126.0cm, standalone (L1/L2) 135.7cm, standalone (C/A) 428.9cm, and SBAS 109.2cm. The results showed that the positioning accuracy of SBAS was comparable to that of DGPS.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.41 no.2
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• pp.134-141
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• 2013

This paper explores a real-time system implementation to couple tightly StrapDown Inertial Navigation System(SDINS) and Global Positioning System(GPS) mounted on the aircraft. When implementing the SDINS/GPS coupled system in real-time processor, we have to deliberate SDINS's unique characteristics based on the ring laser gyro, and besides, lever-arm, measurements, and error compensation method. The novel modeling method is applied to system the misalignment error term of gyro to estimate the cumulative heading attitude errors while the aircraft banking to turn repeatedly. Captive Flight Test results show that the proposed modeling strategy has good performance.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.43 no.1
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• pp.79-87
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• 2015

In this paper, a real time on-board orbit determination method using the extended kalman filter is suggested and its performance is analyzed in the environment of the orbit. Considering the limited on-board resources, the $J_2$ orbit propagate model and the GPS navigation solution are used for on-board orbit determination. The analysis result of the on-board orbit determination method implemented in DubaiSat-2 showed that position and velocity error are improved from 70.26 m to 26.25 m and from 3.6 m/s to 0.044 m/s, respectively when abnormal excursion errors is removed in the GPS navigation solution.

• Journal of Korean Society for Geospatial Information Science
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• v.5 no.1 s.9
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• pp.57-70
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• 1997

Conventional procedures to determine vertical deflections and astronomical coordinates require the stellar observations which be under restraints of clear night-time weather conditions, surrounding environment, long observation time and the use of instruments, etc. Therefore the more effective observation method subjugatting these problems has requested. The objective of this study is to propose method to compute vertical deflections, astronomical coordinates(latitude and longitude), and astronomical azimuth by mixing GPS observation results and orthometric heights. For this study, programmed the program which able to obtain the change in geoid undulation by using the GPS- determined geodetic height difference and the orthometric height difference, and GPS satellite surveying was performed at both ten points of astronomical points and four triangulation points around each astronomical station in South Korea. The Astronomical results determined from GPS observations compared to those determined from both conventional astronomical measurements and the recent earth gravitational Model(EGM96).

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• v.1
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• pp.277-282
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• 2006

It is well known that Kalman filtering is an optimal real-time data fusion method for GPS/INS integration. However, it has some limitations in terms of stability, adaptability and observability. A Kalman filter can perform optimally only when its dynamic model is correctly defined and the noise statistics for the measurement and process are completely known. It is found that estimated Kalman filter states could be influenced by several factors, including vehicle dynamic variations, filter tuning results, and environment changes, etc., which are difficult to model. Neural networks can map input-output relationships without apriori knowledge about them; hence a proper designed neural network is capable of learning and extracting these complex relationships with enough training. This paper presents a GPS/INS integrated system that combines Kalman filtering and neural network algorithms to improve navigation solutions during GPS outages. An Extended Kalman filter estimates INS measurement errors, plus position, velocity and attitude errors etc. Kalman filter states, and gives precise navigation solutions while GPS signals are available. At the same time, a multi-layer neural network is trained to map the vehicle dynamics with corresponding Kalman filter states, at the same rate of measurement update. After the output of the neural network meets a similarity threshold, it can be used to correct INS measurements when no GPS measurements are available. Selecting suitable inputs and outputs of the neural network is critical for this hybrid method. Detailed analysis unveils that some Kalman filter states are highly correlated with vehicle dynamic variations. The filter states that heavily impact system navigation solutions are selected as the neural network outputs. The principle of this hybrid method and the neural network design are presented. Field test data are processed to evaluate the performance of the proposed method.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.8 no.6
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• pp.1443-1448
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• 2007

In this paper, we implement a distributed computing environment-based travel information service that can use web(internet) and speech interface at the same time and can apply location information, using voice and web browser-based VoiceXML and GPS, to escape the limitations of traditional web(internet)-based travel information services. Because of IVR(Interactive Voice Response) of traditional call center has operated to a pre-installation scenario, it takes much a service time and has the inconveniences that must repeat speech recording according to the revised scenarios in case change response contents. However, suggested VoiceXML and GPS-based travel information service system has advantages that reorganization of system setups is easy, because it consists of the method to update server after make individual conversation scenarios by file format(document), and can provide usefully various travel information in environmental restriction conditions such as the back regions environment, according as our prototype find user's present location using GPS information and then provide various travel information service by this information.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.8 no.5
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• pp.1004-1009
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• 2004

Precise time synchronization is a main technology in high-speed communications, parallel and distributed processing systems, Internet information industry and electronic commerce. Synchronized clocks are useful for many leasers. Often a distributed system is designed to realize some synchronized behavior, especially in real-time processing in factories, aircraft, space vehicles, and military applications. Nowadays, time synchronization has been compulsory thing as distributed processing and network operations are generalized. A network time server obtains, keeps accurate and precise time by synchronizing its local clock to standard reference time source and distributes time information through standard time synchronization protocol. This paper describes design issues and implementation of a network time server for time synchronization especially based on a clock model. The system uses GPS (Global Positioning System) as a standard reference time source and offers UTC (universal Time coordinated) through NTP (Network Time protocol). Implementation result and performance analysis are also presented.