• The KIPS Transactions:PartA
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• v.8A no.4
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• pp.429-438
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• 2001

GPS (Global Positioning System) is the most ideal navigation system which can be used on the earth irrespective of time and weather conditions. GPS has been used for various applications such as construction, survey, environment, communication, intelligent vehicles and airplanes and the needs of GPS are increasing in these days. This paper deals with the design and implementation of the RTOS (Real-Time Operating System) for a GPS navigation computer in the GPS/INS integrated navigation system. The RTOS provides the optimal environment for execution and the base platform to develop GPS application programs. The key facilities supplied by the RTOS developed in this paper are priority-based preemptive scheduling policy, dynamic memory management, intelligent interrupt handling, timers and IPC, etc. We also verify the correct operations of all application tasks of the GPS navigation computer on the RTOS and evaluate the performance by measuring the overhead of using the RTOS services.

• Journal of Satellite, Information and Communications
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• v.7 no.2
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• pp.104-109
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• 2012

Currently, GPS(Global Positioning System) is used to find user location information. However, in some cases, especially in urban environments, we receive unreliable location information deu to multipath fading. In order to resolve this problem, we propose a closely coupled positioning technique where GPS signal is combined with QZSS signal. Also we proposed and analyze a combining algorithm of GNSS and Wi-Fi signals to get closely coupled location information by referring AP information. Finally, this paper proposes a combined GPS/QZSS/Wi-Fi navigation algorithm to improve navigation performance, and it is verified by testing of car deriving according to availability and accuracy standard.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2011.06a
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• pp.29-30
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• 2011

GNSS 시스템의 다원화에 따른 DGPS RSIM 기능도 DGNSS 체제로 기능적, 시스템적 고도화가 필요한 시점이 도래하고 있다. 이와 관련하여 차세대 DGNSS RSIM 아키텍처를 미국 해양경비대(USCG) NAVCEN에서 제안하였는데, 이 차세대 DGPS RSIM 아키텍처의 기본 요구조건은 PC 플랫폼 기반의 신규 신호 및 기술에 대한 충분한 유연성을 확보할 수 있고, 기존 사용자 수신기와 기존 기준국 시스템과의 충분한 호환이 가능해야 한다는 것이다. 그러나 위의 제시된 아키텍처는 DGPS RSIM 시스템의 소프트웨어 응용에 초점이 맞추어져 있어서 GNSS 다원화에 따른 DGNSS 기준국 기능 고도화에 한계가 있다. 그러므로 본 논문에서는 소프트웨어 DGNSS RSIM 개발을 위한 후속연구로서, 현재 운영 중인 GPS/GLONASS를 중심으로 보정정보 생성 및 그 측위정확도 성능분석에 중점을 두고자 한다. 기 설계된 DGNSS 소프트웨어 RSIM 아키텍처에 대해 설명하고, 설계된 아키텍처와 통합보정정보 생성 및 처리 기법이 적용된 GPS/GLONASS 통합보정시스템을 구현하여, 향후 소프트웨어 DGNSS RSIM을 위한 측위정확도 측면에서의 성능을 분석한다.

• 한국항공운항학회:학술대회논문집
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• 2004.11a
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• pp.295-301
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• 2004

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.45 no.6
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• pp.77-81
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• 2008

In the deeply coupled GPS/INS integrated systems, if the integration filter update period is longer than the period of GPS navigation data, the loss of correlation values occurs due to the bit transition. This problem can be resolved when data wipe off(DWO) is used. However, general DWO methods requires heavy computation or cannot be applied continuously. This paper proposes an effective DWO method using carrier phase discriminator In order to show validity of the proposed method, simulations were carried out. The simulation results show that the data bit is accurately estimated and conform that the loss of correlation values and the error of code phase is small.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.30 no.1
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• pp.38-43
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• 2022

As the use of unmanned aerial vehicles increases, in order to expand the operability of the unmanned aerial vehicle, it is essential to develop an unmanned aerial vehicle traffic management system, and to establish the system, it is necessary to analyze the integrated navigation performance of the unmanned aerial vehicle to be operated. Integrated navigation performance is affected by various factors such as the type of unmanned aerial vehicle, flight environment, and guidance law algorithm. In addition, since a large amount of flight data is required to obtain high-reliability analysis results, efficient and consistent flight scenarios are required. In this paper, a flight scenario that satisfies the requirements for integrated navigation performance analysis of rotary and fixed-wing unmanned aerial vehicles was designed and verified through flight experiments.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.48 no.4
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• pp.285-293
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• 2020

In this paper, to improve Synthetic Aperture Radar (SAR) image quality, the effect of time synchronization error in the EGI/IMU (Embedded GPS/INS, Inertial Measurement Unit) integrated system is analyzed and state augmentation is applied to compensate it. EGI/IMU integrated system is widely used as a SAR motion measurement algorithm, which consists of EGI mounted to obtain the trajectory and IMU mounted on the SAR antenna. In an EGI/IMU integrated system, a time synchronization error occurs when the clocks of the sensors are not synchronized. Analysis of the effect of time synchronization error on navigation solutions and SAR images confirmed that the time synchronization error deteriorates SAR image quality. The state augmentation is applied to compensate for this and as a result, the SAR image quality does not decrease. In addition, by analyzing the performance and the observability of the time synchronization error according to the maneuver, it was confirmed that the time-variant maneuver such as rotational motion is necessary to estimate the time synchronization error adequately. In order to reduce the influence of the time synchronization error on the SAR image, the time synchronization error must be compensated by performing maneuver changing over time such as a rotation before SAR operation.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37C no.12
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• pp.1310-1317
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• 2012

The Global Navigation Satellite System (GNSS) like US Global Positioning System (GPS) and EU Galileo are based on providing precise time and frequency synchronized ranging signals. Because of the exploitation of very precise timing signals these GNSS are used to provide both navigation and time distribution services. Moreover, because the positioning accuracy will improve as more satellites become available, we should expect that a combination of Galileo and GPS will provide better performance than those of both systems separately. However, Galileo will not use the same time reference as GPS and thus, a time difference arises - the GPS-Galileo Time Offset (GGTO). The navigation solution calculated by receivers using signals from both navigation systems will consequently contain a supplementary error if the GGTO is not accounted for. In this paper, we compared GPS Time (GPST) with Galileo Sytem Time (GST) and analyzed the effects of GGTO on positioning accuracy by simulation test. And then we also analyzed the characteristics of two representative GGTO correction methods such as the navigation message based method at system level and the estimation method at user level and propose the conceptual design of the novel correction method being capable of preventing previous method's problems.

• Journal of the Korea Institute of Military Science and Technology
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• v.12 no.5
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• pp.615-621
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• 2009

Since GPS receivers and INS algorithms do not work properly in the spinning vehicles due to change of the GPS signal and excess of the measurement limitation of the gyroscope, conventional GPS/INS integrated navigation systems do not provide accurate navigation outputs. This paper proposes a design method for GPS/INS integrated navigation systems of spinning vehicles. A special GPS receiver with a signal tracking loop for changed GPS signal caused by spinning and an INS with a roll estimation method are configured and the conventional integration filter is combined. The proposed method was verified through comparison of the navigation results. The result of the proposed method for the spinning vehicle was similar to that of the conventional navigation system without spinning.

• Journal of Korean Society of Transportation
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• v.17 no.3
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• pp.7-20
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• 1999

This Paper Presents a Internet-based Real-Time Automated Vehicle Location System(AVLS), which is able to Provide users with real-time vehicle Positioning information. When Inverted Differential GPS is available, this system does more aggressive position correction than GPS, and more useful for public transportation and commercial application than DGPS in terms of cost.