• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
• /
• v.36 no.6
• /
• pp.621-628
• /
• 2018

More than four visible GPS (Global Positioning System) satellites are required to obtain absolute positioning. However, it is not easy to satisfy this condition when a rover is in such unfavorable condition as an urban area. As a consequence, clock-aided positioning has been used as an alternative method especially when the number of visible satellites is three providing that receive clock error information is available. In this study, LSC (Least-Squares Collocation) method is proposed to interpolate clock errors for clock-aided positioning after analyzing the characteristics of receiver clock errors. Numerical tests are performed by using GPS data collected at one of Korean CORS (Continuously Operating Reference Station) and a nearby GPS station. The receiver clock errors are obtained through the DGPS (Differential GPS) positioning technique and segmentation procedures are applied for efficient interpolation. Then, LSC is applied to predicted clock error at epoch which clock information is not available. The numerical test results are analyzed by examining the differences between the original and interpolated clock errors. The mean and standard deviation of the residuals are 0.24m and 0.49m, respectively. Therefore, it can be concluded that sufficient accuracy can be obtained by using the proposed method in this study.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.19 no.4
• /
• pp.1017-1023
• /
• 2015

The amount of smart phones has increased exponentially. Due to the periodic release of high-performance smart phones and upgraded operating system, new smart phones become out-dated over 1 or 2 years. In order to solve environmental constraints of these smart phones, virtualization technology using Thin-Client terminal has been developed. However, in the case of Virtual Machine(VM), the applications associated with sensors and a GPS device can not run because they are not included. In this paper, by implementing the device driver for Android running in a virtual machine in the x86-based systems, it is to provide Android virtualization capabilities such as using the latest smart phones in the virtual machine environment. It would like to propose a method that the virtual device driver receives sensors and GPS information from the old Android smart phones(Thin-Client) that actually work and run as if the real device exists.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.14 no.7
• /
• pp.1537-1543
• /
• 2010

This paper describes a compact microstrip antenna with dual polarization characteristics. The antenna, receiving both a left-hand circularly polarized(LHCP) wave and a right-hand circularly polarized(RHCP) wave, can be used for a polarization diversity. A diamond-shaped patch with internal empty room is designed for impedance matching as well as size reduction. And slots are added around feeding point to improve input matching. The proposed antenna has been applied to GPS(global positioning system), operating at 1.57GHz. And, the proposed idea has been verified and estimated by simulation. The measurement results show that it has VSWR 2:1 bandwidth of 83MHz, 3dB axial bandwidth of about 58MHz, 3dB beamwidth of 90degree, and gain of 0dBi, respectively, for RHCP. Also, it has similar performances for LHCP.

• Journal of Advanced Navigation Technology
• /
• v.23 no.3
• /
• pp.228-236
• /
• 2019

Recently, multi-sensor integration techniques have been actively studied to obtain reliable and accurate navigation solution in GPS (Global Positioning System)-denied harsh environments such as urban canyons, tunnels, and underground roads. In this paper, we propose a low-cost ultrasonic-speedometer utilizing the characteristics of the ultrasonic propagation. An efficient integrated INS (inertial navigation system)/ultrasonic-speedometer navigation system is also proposed to improve the accuracy of positioning in GPS-denied environments. To evaluate the proposed system, car experiments with field-collected measurements were performed. By the experiment results, it was confirmed that the proposed INS/ultrasonic-speedometer system bounds the positioning error growth effectively even though GPS signal is blocked more than 10 seconds and a low-cost MEMS IMU (micro electro mechanical systems inertial measurement unit) is utilized.

• Journal of the Korean Geophysical Society
• /
• v.10 no.1
• /
• pp.37-44
• /
• 2007

Nowadays, Global Navigation Satellite System(GNSS) which is the new concept of positioning system has been developed because of satisfaction human's intelligent desire and rapid science development. GNSS which is represented by GPS provides 3-Dimension positioning information not expensively in whenever, wherever. The industry of positioning information has extending civil market widely as well as military market. So GNSS is running the role of society infra structure including car and airborne navigation, civil engineering, GIS resource, telematics and LBS, and so on. As USA removes the SA(Selective Availability), GPS has monopolizing the market and other countries have been depended on GPS, absolutely. In this paper, the author developed the software for analysis of influence using next generation, Galileo system. The local analysis was performed according to positioning mode. And GPS/Galileo combined system can implement positioning in the worst mask environment like urban cannon.

• The Journal of The Korea Institute of Intelligent Transport Systems
• /
• v.8 no.4
• /
• pp.84-92
• /
• 2009

In this paper, using the received signal strength of radio beacon such as Wi-Fi, Bluetooth, CDMA and GPS signal from the satellite, we propose the system of positioning which considered indoor and outdoor based on the Place Lab. Conventional Place Lab utilize the various positioning parameters to estimate the indoor location. However, this conventional system has limitations with respect to the range and efficiency of usage. Therefore, we defined the converged model of multisensor data and re-organized the Place Lab to overcome the limitation of a conventional system. Proposed system uses the radio beacon signal and GPS signal together to estimate the location. Furthermore, it provides the seamless PNS service with many mobile devices because this system realized by the OSGi bundle. This proposed system has evaluated the performance with SAMSUNG T*OMNIA SCH-M490 smart phone and the result shows the system is able to support the PNS service.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.40 no.12
• /
• pp.1048-1054
• /
• 2012

This paper presents a Carrier phase fault detection (FD) method for GPS RTK (Global Positioning System Real Time Kinematic) in dynamic environment. There are various error sources in dynamic environment and these errors decrease the reliability of FD results. Due to the reason, Carrier phase measurements are separated into satellite induced signal, user induced signal and other remaining errors. Especially the user-induced signal is computed by user dynamic which is estimated by time-differenced Carrier phase (TDCP) and Doppler shift. TDCP makes it possible to avoid integer ambiguity resolution. Computer simulation is conducted to verify the suggested method. By applying impulse, step and ramp faults, the FD performance is analyzed.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.18 no.10
• /
• pp.2530-2536
• /
• 2014

Many studies have been made on location estimation under indoor environments which GPS signals do not reach, and, as a result, a variety of estimation methods have been proposed. In this paper, we deeply consider a problem of location estimation in a ship with a multi-story structure, and investigate a location estimation method using the fingerprint scheme based on the K-Nearest Neighbor algorithm. A reliable DB is constructed by measuring 100 received signals at each of 39 RPs in order to employ the fingerprint scheme, and, based on the DB, a simulation to estimate the location of a randomly-positioned terminal is performed. The simulation result confirms that the performance of location estimation by the fingerprint scheme is quite satisfactory.

• Journal of Advanced Navigation Technology
• /
• v.21 no.3
• /
• pp.272-278
• /
• 2017

In order to meet performance requirements specified by the ICAO in drone operation, a system that provides augmentation information such as SBAS is needed. However, the operating range of the drone is limited in situation where the drone can not received the SBAS message continuously. In this paper, we propose a system to transmit SBAS augmentation message using a separate communication channel assuming the SBAS satellite signal to the drone has been shielded. We implemented the proposed system and verified its performance in the static environment. The DGPS positioning results showed that the accuracy difference is about 10cm, which means the accuracy performance was very similar. In addition, the protection level calculated by the system also shows the difference within 2m from the value calculated by the airborne receiver.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.13 no.1
• /
• pp.59-65
• /
• 2012

The study conducted the measurement of RTK-GPS with changing the number of observation as the method to differ reference stations of RTK-GPS. Also it aimed to suggest an effective application plan for cadastral surveying based on the accuracy analysis accordingly. According to the result of selecting the study region, observing with different reference stations, and comparing with previous TS performance, the 1st reference station was calculated as ${\pm}0.024m$ for x-coordinate's RMSE and ${\pm}0.029m$ for y-coordinate's RMSE, and the 2nd reference station was calculated as ${\pm}0.040m$ for x-coordinate's RMSE and ${\pm}0.029m$ for y-coordinate's RMSE. All these results (the 1st and the 2nd reference stations) are allowed as acceptable performance within the margin of error according to the existing cadastral regulations, and there was no significant difference between two performances. Therefore, unless there was no problem in receiving GPS satellite data, it would be possible to secure stable performance enough with 1 observation. Depending on surveying environment that has possible problems in receiving data, however, 2 or more observations would be necessary to secure stable performance.