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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Journal of Positioning, Navigation, and Timing
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Journal DOI :
The Korean GNSS Society
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Volume & Issues
Volume 1, Issue 1 - Oct 2012
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Performance Analysis of a Vector DLL Based GPS Receiver
Lim, Deok Won ; Choi, Heon Ho ; Lee, Sang Jeong ; Heo, Moon Beom ;
Journal of Positioning, Navigation, and Timing, volume 1, issue 1, 2012, Pages 1~6
DOI : 10.11003/JKGS.2012.1.1.001
For a Global Positioning System (GPS) receiver, it is known that a Vector Delay Locked Loop (DLL) in which the code signals of each satellite are tracked in parallel by using navigation results shows better performance in the aspect of the tracking accuracy and the robustness than that of a Scalar DLL. However, the quantitative analysis and the logical grounds for that performance enhancement of the Vector DLL are not sufficient. This paper, therefore, proposes the structure of the GPS receiver with the Vector DLL and analyzes the performance of it. The tracking and the positioning accuracy of the Vector DLL are theoretically analyzed and confirmed by simulation results. From the simulation results, it can be seen that the tracking and positioning accuracy has been improved about 30% in case that the receiver is static and the positioning is conducted for every Pre-detection Integration Time (PIT) while C/N0 is 45 dB-Hz.
Carrier Phase Based Navigation Algorithm Design Using Carrier Phase Statistics in the Weak Signal Environment
Park, Sul Gee ; Cho, Deuk Jae ; Park, Chansik ;
Journal of Positioning, Navigation, and Timing, volume 1, issue 1, 2012, Pages 7~14
DOI : 10.11003/JKGS.2012.1.1.007
Due to inaccurate safe navigation estimates, maritime accidents have been occurring consistently. In order to solve this, the precise positioning technology using carrier phase information is used, but due to high buildings near inland waterways or inclination, satellite signals might become weak or blocked for some time. Under this weak signal environment for some time, the GPS raw measurements become less accurate so that it is difficult to search and maintain the integer ambiguity of carrier phase. In this paper, a method to generate code and carrier phase measurements under this environment and maintain resilient navigation is proposed. In the weak signal environment, the position of the receiver is estimated using an inertial sensor, and with this information, the distance between the satellite and the receiver is calculated to generate code measurements using IGS product and model. And, the carrier phase measurements are generated based on the statistics for generating fractional phase. In order to verify the performance of the proposed method, the proposed method was compared for a fixed blocked time. It was confirmed that in case of a weak or blocked satellite signals for 1 to 5 minutes, the proposed method showed more improved results than the inertial navigation only, maintaining stable positioning accuracy within 1 m.
A GNSS Interference Detection Method Based on Multiple Ground Stations
Kim, Sun Young ; Kang, Chang Ho ; Yang, Jeong Hwan ; Park, Chan Gook ; Joo, Jung Min ; Heo, Moon Beom ;
Journal of Positioning, Navigation, and Timing, volume 1, issue 1, 2012, Pages 15~21
DOI : 10.11003/JKGS.2012.1.1.015
For a GNSS receiver's robustness against RFI and the high accuracy of navigation solution in GNSS, interference source detection and mitigation are needed. In this paper, an adaptive lattice IIR notch filter is employed to track single-tone continuous wave and swept continuous wave interference signals, and an interference detection method is proposed. Furthermore, this paper presents interference source characterization algorithm using multiple ground stations' interference detection results. The measurement of the signal powers from each ground station is used to build weighting factors to estimate the type of the interference. The performance of interference detection algorithm is simulated for scenarios of GPS signal in the presence of single-tone continuous wave interference and swept continuous wave interference.
Design of an Enhanced TDOA Method for Swept CW Interferences
Kang, Hee Won ; Lim, Deok Won ; Heo, Moon Beom ;
Journal of Positioning, Navigation, and Timing, volume 1, issue 1, 2012, Pages 23~27
DOI : 10.11003/JKGS.2012.1.1.023
Recently, devices like Personal Privacy Devices (PPD) are being employed to avoid the detection of one's location by GPS, and most PPD transmits swept CW signals. However, signals transmitted from PPD may interfere a precise location system based on GPS. Accordingly, in order to reduce interferences by PPD, a technique to locate an interferer is needed. In order to locate an interferer AOA method and TDOA method are generally used, TDOA method is known to be more accurate than AOA method. Unfortunately, TDOA method has a problem of ambiguity in obtaining measurements of swept CW interference. Thus, this paper design a localization algorithm based on TDOA method that can accurately locate an interferer transmitting swept CW signals by resolving problem of ambiguity. In addition, feasibility of the designed algorithm has been verified by simulation results.
Design of Component-Based GNSS Multi-Band IF Signal Generator
Cho, Sung Lyong ; Lim, Deok Won ; Yeo, Sang-Rae ; Park, Chansik ; Hwang, Dong-Hwan ; Lee, Sang Jeong ;
Journal of Positioning, Navigation, and Timing, volume 1, issue 1, 2012, Pages 29~34
DOI : 10.11003/JKGS.2012.1.1.029
A software GNSS signal generator for the GPS L1/L2/L5 and Galileo E1/E5 signals is proposed in this paper. And this signal generator is designed and implemented with several components by considering the reuse and expansion of components for similar GNSS signals. The characteristics of the reusability of the components are confirmed with the carrier generation and the band-pass filter components. And the functionality of the GNSS multi-band IF signal generator is validated by using the commercial software GPS L1 receiver, and the performance of signal acquisition, tracking and accuracy of horizontal position error are analyzed for this validation. As a result, the GPS L1 signal generator operates successfully and it could be expected that other signal generators also operate well because most of components are the same as those of the GPS L1 signal generator.
Design of Multi-Sensor-Based Open Architecture Integrated Navigation System for Localization of UGV
Choi, Ji-Hoon ; Oh, Sang Heon ; Kim, Hyo Seok ; Lee, Yong Woo ;
Journal of Positioning, Navigation, and Timing, volume 1, issue 1, 2012, Pages 35~43
DOI : 10.11003/JKGS.2012.1.1.035
The UGV is one of the special field robot developed for mine detection, surveillance and transportation. To achieve successfully the missions of the UGV, the accurate and reliable navigation data should be provided. This paper presents design and implementation of multi-sensor-based open architecture integrated navigation for localization of UGV. The presented architecture hierarchically classifies the integrated system into four layers and data communications between layers are based on the distributed object oriented middleware. The navigation manager determines the navigation mode with the QoS information of each navigation sensor and the integrated filter performs the navigation mode-based data fusion in the filtering process. Also, all navigation variables including the filter parameters and QoS of navigation data can be modified in GUI and consequently, the user can operate the integrated navigation system more usefully. The conventional GPS/INS integrated system does not guarantee the long-term reliability of localization when GPS solution is not available by signal blockage and intentional jamming in outdoor environment. The presented integration algorithm, however, based on the adaptive federated filter structure with FDI algorithm can integrate effectively the output of multi-sensor such as 3D LADAR, vision, odometer, magnetic compass and zero velocity to enhance the accuracy of localization result in the case that GPS is unavailable. The field test was carried out with the UGV and the test results show that the presented integrated navigation system can provide more robust and accurate localization performance than the conventional GPS/INS integrated system in outdoor environments.
Comparison Between DCM and Quaternion Transformation in Lever Arm Compensation of Reference System for Flight Performance Evaluation of DGPS/INS
Park, Ji-Hee ; Shin, Dong-Ho ;
Journal of Positioning, Navigation, and Timing, volume 1, issue 1, 2012, Pages 45~49
DOI : 10.11003/JKGS.2012.1.1.045
The flight performance evaluation of navigation system is very significant because the reliability of navigation data directly affect the safety of aircraft. Especially, the high-level navigation system such as DGPS/INS, need more precise flight performance evaluation method. The performance analysis is evaluated by comparing between the navigation system in aircraft and reference trajectory which is more precise than navigation system in aircraft. In order to verify DGPS/INS performance of m-level, the GPS receiver, which is capable post-processed Carrier-phase Differential GPS(CDGPS) method of cm-level, have to be used as reference system. The DGPS/INS is estimated the Center of Gravity (CG) point of aircraft to offer precise performance while the reference system is output the position of GPS antenna which is mounted on the outside of aircraft. Therefore, in order to more precise performance evaluation, it needs to compensate the lever arm and coordinates transformation. This paper use quaternion and Direct Cosine Matrix(DCM) methods as coordinate transformation matrix in lever arm compensation of CDGPS reference trajectory. And it compares NED errors of DCM and quaternion transformation in lever arm of reference trajectory via DGPS/INS result.
Design of an Error Model for Performance Enhancement of MEMS IMU-Based GPS/INS Integrated Navigation Systems
Koo, Moonsuk ; Oh, Sang Heon ; Hwang, Dong-Hwan ;
Journal of Positioning, Navigation, and Timing, volume 1, issue 1, 2012, Pages 51~57
DOI : 10.11003/JKGS.2012.1.1.051
In this paper, design of an error model is presented in which the bias characteristic of the MEMS IMU is taken into consideration for performance enhancement of the MEMS IMU-based GPS/INS integrated navigation system. The drift bias of the MEMS IMU is modeled as a 1st-order Gauss-Markov (GM) process, and the autocorrelation function is obtained from the collected IMU data, and the correlation time is estimated from this. Prior to obtaining the autocorrelation function, the noise of IMU data is eliminated based on wavelet. As a result of simulation, it is represented that the parameters of error model can be estimated correctly only when a proper denoising is performed according to dynamic behavior of drift bias, and that the integrated navigation system based on error model, in which the drift bias is considered, provides more correct navigation performance compared to the integrated navigation system based on error model in which the drift bias is not considered.
Precise Orbit Determination of GRACE-A Satellite with Kinematic GPS PPP
Choi, Byung-Kyu ; Roh, Kyoung-Min ; Yoo, Sung-Moon ; Jo, Jung-Hyun ; Lee, Sang-Jeong ;
Journal of Positioning, Navigation, and Timing, volume 1, issue 1, 2012, Pages 59~64
DOI : 10.11003/JKGS.2012.1.1.059
Precise Point Positioning (PPP) has been widely used in navigation and orbit determination applications as we can obtain precise Global Positioning System (GPS) satellite orbit and clock products. Kinematic PPP, which is based on the GPS measurements only from the spaceborne GPS receiver, has some advantages for a simple precise orbit determination (POD). In this study, we developed kinematic PPP technique to estimate the orbits of GRACE-A satellite. The comparison of the mean position between the JPL's orbit product and our results showed the orbit differences 0.18 cm, 0.54 cm, and 0.98 cm in the Radial, in Along-track, and Cross-track direction respectively. In addition, we obtained the root mean square (rms) values of 4.06 cm, 3.90 cm, and 3.23 cm in the satellite coordinate components relative to the known coordinates.
A Comparison of Broadcast and Final Orbits on GPS Delays in GPS-VLBI Hybrid Observation
Kwak, Younghee ; Cho, Jungho ; Kondo, Tetsuro ; Takiguchi, Hiroshi ; Amagai, Jun ; Gotoh, Tadahiro ; Sekido, Mamoru ; Ichikawa, Ryuichi ; Kim, Tuhwan ; Sasao, Tetsuo ;
Journal of Positioning, Navigation, and Timing, volume 1, issue 1, 2012, Pages 65~75
DOI : 10.11003/JKGS.2012.1.1.065
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.