• Journal of Astronomy and Space Sciences
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• v.35 no.4
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• pp.287-293
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• 2018

This paper presents a satellite relative navigation strategy for formation flying, which chooses an appropriate navigation algorithm according to the operating environment. Not only global positioning system (GPS) measurements, but laser measurements can also be utilized to determine the relative positions of satellites. Laser data is used solely or together with GPS measurements. Numerical simulations were conducted to compare the relative navigation algorithm using only laser data and laser data combined with GPS data. If an accurate direction of laser pointing is estimated, the relative position of satellites can be determined using only laser measurements. If not, the combined algorithm has better performance, and is irrelevant to the precision of the relative angle data between two satellites in spherical coordinates. Within 10 km relative distance between satellites, relative navigation using double difference GPS data makes more precise relative position estimation results. If the simulation results are applied to the relative navigation strategy, the proper algorithm can be chosen, and the relative position of satellites can be estimated precisely in changing mission environments.

• Journal of the Korea Society of Computer and Information
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• v.17 no.8
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• pp.41-50
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• 2012

Most of the developed countries and Korea have continued to invest much money in developing low-carbon vehicles such as electric car, methanol car and hydrogen car to replace the conventional fossil fuel vehicles. Government and local governments of each country, however, grope to construct roads for bicycle and public bicycle rental systems because bicycle is the only ultimate and feasible non-pollution transportation. Most of the current bicycle monitoring systems have achieved automation of rental process in bicycle stations, but they can not monitor bicycles in use. This paper develops GPS-CDMA modem combined terminals and implements a LBS-based bicycle monitoring system using them for public bicycle rental system. The monitoring system collects location information from GPS-CDMA modem combined terminals attached on bicycles and presents the moving tracks of bicycles on a GIS map for easy return and redistribution of bicycles. Also, the system helps to prevent from theft and vandalism of bicycles and to recommend the nearest bicycle station.

• Journal of Satellite, Information and Communications
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• v.11 no.2
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• pp.8-13
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• 2016

A buoy is a float attached by chain to the seabed to mark channels in a harbor or underwater hazards and can be classified into two major types as autonomous buoys and fixed buoys. When there is high demand such as marking channels in a harbor, monitoring ecology of ocean and environmental monitoring of coastal areas, smart buoys are developed. The smart buoys have wireless network systems such as GPS, CDMA and ZigBee. Using the GPS techniques, location and environments of buoy can be monitored and traced. However, the GPS in fixed buoy systems has a high power consumption and cost. Using many buoys on low power ZigBee basis allows dramatic reduction of the overall power consumption. In this study, it is aimed at the design of the trackable protocol for a buoy system which has low data rate and low power consumption. The proposed protocol has advantages that it can detect abnormal movement and gather trackable information without any system changes. In the introduced protocol, additional 2 bits and join request messages are used for trackable buoy system. The behaviors of improved protocol is modeled into petri-net and proved a reachability.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.4
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• pp.632-637
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• 2016

A streetlight control system was developed using information technology and LED lights for efficient management and energy savings. The proposed system can control the power usage of an LED streetlight luminaire using GPS satellite communication and an Arduino with a built-in microprocessor. A control circuit was designed to control the current using GPS, a control unit, transistor, resistor, and constant-current supply circuit. The circuit was validated through experiments with normal operation. Using GPS, the control system extracts accurate time and location information according to the season, and it controls the current supplied to the LED streetlight according to the extracted time. Power consumption was reduced by more than 11%. The control system could reduce accidents caused by conventional lighting systems used to save energy, and it could improve the inefficient management of energy by preserving constant brightness of a streetlight at times and in areas that have less traffic.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.39 no.3
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• pp.192-203
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• 2016

Uganda is a country blessed with the biggest number of mountain Gorillas in the whole world. These animals contribute at least 12% in revenue generation to the Tourism sector through tracking by both local and foreign tourists who pay for the tracking permits. However, Gorilla tracking is also a big challenge even in the presence of highly skilled and well-trained game rangers. Development and implementation of a secure Computer and Mobile based Gorilla Tracking (GT) system that uses GIS and GPS technologies would be the most ideal technology to use. Therefore, this study aimed to find out the critical factors that would affect the Behavioral Intention of the would-be users to successfully decide to use such GIS/GPS-GT system. We used the existing UTAUT model to integrate six factors such as Performance Expectancy, Effort Expectancy, Employee Peer Influence, Facilitating Conditions, Behavioral Intention and System Use. However, Infrastructure Availability and Non-Technical Facilitating Conditions were added to reflect Ugandan ICT context. This amended UTAUT model was used to carry out the survey. The questionnaire was emailed to 220 government employees in the fields of ICT, Tour and Travel, Environmental Groups officials and Farmers who garden near the game reserves. A total of 133 were obtained fully completed, whereas 127 were deemed usable thus yielding a response rate of 58%. The analysis results show that except for non-technical facilitating conditions, effort expectancy, peer influence, performance expectancy and infrastructure availability positively affects behavioral Intention to use GIS/GPS-GT. This indicates that people in Uganda don't bother about regulations and rules in regard to using information system. As long as the system does what they want it to, anything else does not matter. As an employee in an organization is told to use a system by their supervisor, they have no objection to otherwise they risk losing their job. This implies that, supervisors have a great responsibility in the process of developing, implementing and using the system in Uganda.

• Journal of Institute of Control, Robotics and Systems
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• v.19 no.2
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• pp.87-94
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• 2013

UKF (Unscented Kalman Filter) has been used in the nonlinear systems without initial accurate state estimates instead of EKF (Extended Kalman Filter) of the last decade because the UKF has robustness to the large initial estimation error. In the multirate integrated system such as INS (Inertial Navigation System)/GPS (Global Positioning System) integrated navigation system, however, it is difficult to implement the UKF based navigation algorithm in the mid-grade micro-processor due to the large computational burden. To overcome this problem, this paper proposes a MUKF (Modified UKF) that has a reduced computation burden using the basic idea that the change of the provability distribution for the state variables between measurement updates is small in the multi-rate INS/GPS integrated navigation filter. The performance of the proposed MUKF is verified by numerical simulations.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2016.05a
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• pp.612-613
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• 2016

Today, a variety of systems have been developed to protect women and children. However, crime rates are still rising in the Green Zone. So we need the system to protect it. In this paper, we propose a system that sends messages in real time to the Green Zone administrator when a registered offender access to the Green Zone area. The existing system is a passive data transmission through monitoring. But the proposed system when access to the Green Zone set, detects a GPS-based. Accordingly, It is expected to be able protection through to monitor in real time and manage for women and children from criminals.

• Journal of Positioning, Navigation, and Timing
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• v.1 no.1
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• pp.65-75
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• 2012

We carry out an error analysis of 24-hour global positioning system (GPS)-very long baseline interferometry (VLBI) (GV) hybrid observation data. In this paper, we focus on the impacts of broadcast and final orbits on the GPS delays of the GV hybrid observation by analyzing the residuals, observed - calculated (O-C) values. The residuals show apparent and consistent biases for L1 and L2 signals, respectively. The scatters of the residuals are around a few nanoseconds. The main cause of those observation errors is the absence of the GPS phase and delay calibration system. Most of the satellites show that the differences between the delays, to which broadcast and final orbits are applied, are about 100 times smaller than the current GV hybrid observation errors. We conclude that GPS delays are not greatly affected by orbit accuracies.

• The Journal of Korea Robotics Society
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• v.19 no.1
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• pp.23-30
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• 2024

This paper studies a GPS error filtering method that takes into account the continuity of the ongoing path to enhance the safety of autonomous agricultural mobile robots. Real-Time Kinematic Global Positioning System (RTK-GPS) is increasingly utilized for robot position evaluation in outdoor environments due to its significantly higher reliability compared to conventional GPS systems. However, in orchard environments, the robot's current position obtained from RTK-GPS information can become unstable due to unknown disturbances like orchard canopies. This problem can potentially lead to navigation errors and path deviations during the robot's movement. These issues can be resolved by filtering out GPS information that deviates from the continuity of the waypoints traversed, based on the robot's assessment of its current path. The contributions of this paper is as follows. 1) The method based on the previous waypoints of the traveled path to determine the current position and trajectory. 2) GPS filtering method based on deviations from the determined path. 3) Finally, verification of the navigation errors between the method applying the error filter and the method not applying the error filter.

• The Journal of the Acoustical Society of Korea
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• v.12 no.1
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• pp.61-73
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• 1993

위치, 속도 및 시간측정을 정확하게 수행하는 GPS 기술이 최근들어 일반 사용자들에게 널리 활용되는 추세에 있다. 본 고에서는 GPS 기술의 일반적인 내용과 수신기 구성에 필요한 요소기술을 소개한다. 한편, 국내외 기술개발의 동향을 분석한다.