• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.26 no.5D
• /
• pp.731-738
• /
• 2006

Facing congestion, people want to know traffic information about their routes, especially real-time link travel time (LTT). In this paper, as a sequel paper of the previous non-taxi based LTT generating study by Choi et al. (1998), taxi based GPS probes have been tried to produce LTT for urban arterials. Taxis in itself are good deployment mode of GPS probes although it by nature experiences boarding and alighting time noises which should be accounted. A heuristic real-time dynamic outlier filter algorithm for taxi GPS probe has been developed focusing on urban arterials. An actual traffic survey for dynamic link travel times has been conducted using license plate method for the test arterials of Seoul city transportation network. With the algorithm, it is estimated that 70% of outliers have been filtered and the relative error has been improved by 73.7%. The filtering algorithm developed here would be expected to be in use for other spatial sites with some calibration efforts. Some limitations and future research agenda have also been discussed.

• Journal of Positioning, Navigation, and Timing
• /
• v.13 no.1
• /
• pp.53-61
• /
• 2024

Global Navigation Satellite Systems are expected to meet system-defined integrity requirements when users utilize the system for safety critical applications. While the guaranteed integrity performance of GPS and Galileo is publicly available, their integrity assurance procedure and related methodology have not been released to the public in an official document format. This paper summarizes the integrity assurance procedures of Global Positioning System (GPS) and Galileo, which were utilized during their system development, through a literature survey of their integrity assurance methodology. GPS Block II assures system integrity using the following methods: continuous performance monitoring and maintenance on Space Segment (SS) and Control Segment (CS), through a cause and effect analysis of anomalies and a failure analysis. In GPS Block III, to achieve more stringent integrity performance, safety requirements are integrated into the system design and development from its starting phase to the final phase. Galileo's integrity performance is provided in the Integrity Support Message (ISM) format, as Galileo utilizes a Dual Frequency Multi Constellation (DFMC) Satellite Based Augmentation System (SBAS) and Advanced Receiver Autonomous Integrity Monitoring (ARAIM) to serve safety critical applications. The integrity performance of Galileo is ensured by using a methodology similar to GPS Block II (i.e. continuous performance monitoring and maintenance on the system). The integrity assurance procedures reviewed in this paper can be utilized for a new satellite navigation system that will be developed in the near future.

• Proceedings of the Korean Society of Coastal and Ocean Engineers Conference
• /
• 2000.09a
• /
• pp.84-87
• /
• 2000

최근 들어 구조물이 대형화되고 급속히 시공되는 경향이 증가함에 따라 구조물에 대한 변위측정은 시공중인 구조물뿐만 아니라, 그 사후관리 및 안전성 여부를 파악하는데 중요한 기초자료로 활용되고 있다. 특히, 해상에서 실시되는 방조제나 안벽 공사 등에서는 육상구조물에 비해 변위측정에 여러 가지 제약이 따른다. 이와 같은 해상 토목구조물의 거동을 다각적으로 파악하기 위한 연직 방향 및 평면 변위 측정에 GPS를 적용하면 신속하고 정확한 변위측정 자료를 획득할수 있다. (중략)

• Proceedings of the Korean Society of Surveying, Geodesy, Photogrammetry, and Cartography Conference
• /
• 2003.10a
• /
• pp.21-26
• /
• 2003

The fact on a variety of the plane coordinate systems in cadastral survey field caused a troublesome stage by different standards for the production of cadastral maps. The cadastral maps with different origins are not standardized in terms of unit and coordinate system, which introduces surveying problems at the edges where two or more zones meet. Moreover, difficulties in the creation of seamless digital cadastral map DBs between different coordinate systems has become the obstacle to establish various levels of spatial information systems for the efficient management of Korean Peninsula. Therefore, the aim of the study is to present a way to mutual coordinate transformation by clarifying the systematic differences between the areas of different origins.

• Journal of Korean Society for Geospatial Information Science
• /
• v.24 no.2
• /
• pp.113-120
• /
• 2016

The necessity of maritime sector for continuous management, accurate and update location information such as seabed shape and location, research on airborne LiDAR bathymetry surveying techniques are accelerating. Airborne LiDAR systems consist of a scanner and GPS/INS. The location accuracy of 3D point data obtained by a LiDAR system is determined by external orientation parameters. However, there are problems in the synchronization between sensors should be performed due to a variety of sensor combinations and arrangement. To solve this issue, system calibration should be conducted. Therefore, this study evaluates the system verification methods, processes, and operation techniques.

• Electronics and Telecommunications Trends
• /
• v.36 no.4
• /
• pp.61-71
• /
• 2021

Navigation satellite systems (GPS, GLONASS etc.) provide three main services, i.e., positioning for location based services, navigation for multi-modal transportation services, and timing for communication and critical infrastructure services. They were started as military systems but were extended to civil service. Navigation satellite navigation system began with GPS in the USA and GLONASS in Russia at nearly the same time. Indian NavIC and Chines BDS announced their FOCs in 2016 and 2020, respectively and European Galileo and Japanese QZSS are catching up others. In these days, Navigation Satellite System, Positioning, Navigation, and Timing services are part of our daily life very closely. They are required for autonomous driving car, Unmanned vehicles like UAV, UGV, and UMV, 5G/6G telecommunications, world financial system, power system, survey, agriculture, and so on. The services among navigation satellite systems are very competitive and also cooperative one another. This article describes the status of these systems and evolution in the technical and service senses, which may be helpful for planning korea positioning system(KPS).

• 한국ITS학회:학술대회논문집
• /
• 2003.11a
• /
• pp.52-55
• /
• 2003

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
• /
• v.17 no.1
• /
• pp.21-32
• /
• 1999

Mapping and precise point determination by photogrammetry have been shown to be an economic solution. But control points are necessary to determine the exterior orientation parameters. Although the number of required control points has been reduced based on extended bundle adjustment and reinforced cross-strip, the ground survey is a significant factor of whole expenses in photogrammetry. The status of GPS-photogrammetry with kinematic DGPS-positioning to overcome this disadvantages, is now steadly progressive since the first possibility has been proved. The completed satellite configuration, powerful receiver function and upgraded software for kinematic DGPS-positioning have extensively improved the accuracy of combined bundle adjustment. So the research for the operational use of GPS-photogrammetry is absolutely necessary. The presented test field was designed for identification of subsidences in a coal mining area, flown with 60％ sidelap and cross strips. Just with 6 control points and combined block adjustment instead of the traditionally used 21 horizontal and 81 vertical control points the same ground accuracy has been reached. The accuracy of kinematic GPS-positioning and combined block adjustment was independent upon the distance of the ground reference station. It also has been showed that the special model for the systematic error correction in the combined block adjustment.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.19 no.8
• /
• pp.1464-1474
• /
• 1994

GPS(Global Positioning System)is a satellite-based navigation system that we can survey where we are, anywhere and anytime. In this paper, delay-lock loop of the receiver which detects the navigation data is theoretically analyzed, and designed using the digital logic circuit. Also logic operations for the synchronization are analyzed. The designed system consists of the correlator which correlates the received C/A code and the generated C/A code in the receiver, the C/A code generator which generates C/A code of selected satellite, and the direct digital clock syntheizer which generates the clock of the C/A code generator to control the C/A code phase and clock rate. From the analyses results of the proposed digital delay-lock loop system, the system has the detection propertied over 90% when its input signal power is above-113.98dB. The influence of input signal variation of digital delay loop, which is the input of A/D converter, is investigated and the performance is analyzed with the variation of threshold level via the computer simulation. The logic simulation results show that the designed system detects precisely the GPS navigation data.

• Journal of Korean Society for Geospatial Information Science
• /
• v.15 no.3
• /
• pp.87-96
• /
• 2007

In the numerical cadastral surveying field, the cadastral surveying would be measured with the Total Station surveying (electronic plane table surveying) system that consist the Total Station for surveying and the computing system for recording and editing the measured coordinates data by the TS. This study would suggest the advanced method, which is used on the RTK-GPS instead of TS for surveying and the computing system for handling the coordinates data and mapping. As a result of this study, although the measurement accuracy of the RTK-GPS and TS surveying make no greate difference, the suggested method reduces the cost of time and work force with the TS surveying. Besides, the new survey method would be more efficient due to directly handling the data and mapping in the field.