• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.40 no.12
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• pp.1048-1054
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• 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 Korean Society for Aeronautical & Space Sciences
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• v.33 no.6
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• pp.45-50
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• 2005

To determine precise position GPS carrier phase measurements are used. In addition, the multi-antenna system consisting of 2 or more GPS antennas can make attitude determination effectively. When GPS carrier phase measurements are used the integer ambiguity must be fixed. The success rate is used to validate the integer ambiguity. For LEO satellite attitude determination the double difference carrier phase measurements are used, the success rate is calculated using the covariance matrix and the measurement matrix. The constraint that LEO satellite position vector and attitude vector is orthogonal is suggested for improving the success rate. The LEO satellite orbit model is KITSAT3. The results of the simulation are shown and analyzed.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.32 no.9
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• pp.88-93
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• 2004

A method is suggested for validating the existence of bias error on GPS carrier measurement. The baseline constraint is used as an addition measurement, which augments the original measurement equation. The detection probability is calculated on both cases. The first case is using GPS carrier measurement only, the second case is using GPS carrier and a baseline constraint. The improvement of the detection probability is shown, and the advantage of using baseline constraint is described statistically, the results of the simulation is shown and analyzed.

• Journal of Electrical Engineering and Technology
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• v.7 no.3
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• pp.429-435
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• 2012

In this study, a real-time architecture for the detection of clock jumps in the GPS clock behavior is proposed. GPS satellite atomic clocks have characteristics of a second order polynomial in the long term showing sudden jumps occasionally. As satellite clock anomalies influence on GPS measurements which could deliver wrong position information to users as a result, it is required to develop a real time technique for the detection of the clock anomalies especially on the real-time GPS applications such as aviation. The proposed strategy is based on Teager Energy operator, which can be immediately detect any changes in the satellite clock bias estimated from GPS carrier phase measurements. The verification results under numerous cases in the presence of clock jumps are demonstrated.

• Journal of the Korean Institute of Navigation
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• v.6 no.1
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• pp.1-18
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• 1982

In this paper, author studied on the elementary data required for the design of the receiver of Pseudo Noise (PN) phase modulation communication adopted in Global Positioning System(GPS). By computer simulation technique, the phase modulator, filters, and PN generator are designed, and also required bandwidth of R-F amplifier for carrier frequency in phase modulation system is investigated. It is verified that the optimum bandwidth is about 3 times of the PN frequency and almost independent of the carrier frequency. And the low pass filter required for demodulation of slow Boolean data is also found to be about 60 times of the data signal frequency.

• Korean Journal of Geomatics
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• v.3 no.2
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• pp.129-140
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• 2004

This paper addresses solutions th the challenges of carrier phase integer ambiguity resolution and cycle slip detection/identification, for maintaining high accuracy of an integrated GPS/Pseudolite/INS system. Such a hybrid positioning and navigation system is an augmentation of standard GPS/INS systems in localized areas. To achieve the goal of high accuracy, the carrier phase measurements with correctly estimated integer ambiguities must be utilized to update the system integration filter's states. The contribution presents an effective approach to increase the reliability and speed of integer ambiguity resolution through using pseudolite and INS measurements, with special emphasis on reducing the ambiguity search space. In addition, an algorithm which can effectively detect and correct the cycle slips is described as well. The algorithm utilizes additional position information provided by the INS, and applies a statistical technique known as th cumulative-sun (CUSUM) test that is very sensitive to abrupt changes of mean values. Results of simulation studies and field tests indicate that the algorithms are performed pretty well, so that the accuracy and performance of the integrated system can be maintained, even if cycle slips exist in the raw GPS measurements.

• Journal of Positioning, Navigation, and Timing
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• v.4 no.1
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• pp.25-31
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• 2015

In this paper, we described the timing-offset comparison results between various daily jump compensation methods for GPS carrier phase (CP) measurement data. For the performance comparison, we used about 70 days GPS measurement data obtained from two GPS geodetic receivers which share the reference 1 PPS and RF signals and closely located in each other within a few meters. From the experiment results, the followings were observed. First, daily jumps existed in CP measurements depend on not only the environment but also the receiver which will make a full compensation be very hard or impossible. Second, clock bias can be occurred in the case of using a simple compensation with accumulation of daily jumps but it could be used in a short-period frequency comparison campaign (less than about 7 days) despite of its drawback.

• Journal of the Korea Institute of Military Science and Technology
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• v.6 no.1
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• pp.91-107
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• 2003

A 2-dimensional search process in the time and frequency domain is required to acquire the GPS signal, when the code phase and the carrier Doppler for the specified GPS satellite signal are unknown. This paper proposes a new scheme, called Squared-D Searching Method, which can reduce the number of carrier frequency candidates, and a new scheme, named extended Multiple Correlator(XMC), which can reduce the number of code phase candidates. The Squared-D Searching Method can take the twice of Doppler frequency, therefore it can find carrier frequency candidates. The XMC is different from the general multiple correlator in that a combined form of the locally generated codes is used for despreading. Also, this paper tries to analyze a signal detection probability of a GPS receiver under more realistic environments. The result shows that lower detection probability can be obtained when the phase differences among the codes are larger in the correlation arms of a multiple correlator. This phenomenon is not easy to explain with the previous results. And besides, the result shows that proposed acquisition schemes give better performance than a conventional acquisition scheme.

• Proceedings of the KIEE Conference
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• 2001.07d
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• pp.2075-2077
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• 2001

For precise positioning, GPS carrier measurements are often used. In this case, accurate position having mm${\sim}$cm error can be obtained. For 3D positioning, in CDGPS, more than five carrier phase measurements are required. When GPS signals are blocked or carrier phase measurements are insufficient, it cannot provide positioning solution. By integrating CDGPS with INS, continuity of positioning solution can be guaranteed. However, when a vehicle moves in low speed or in stationary, the CDGPS/INS integrated system is difficult to compensate INS attitude errors because GPS velocity error become relatively lange. In this paper, we used the 3D attitude GPS receiver to compensate the INS attitude error. By field experiments, it is shown that the proposed integration system maintains the navigation performance even when a vehicle is in low speed or GPS signal is blocked for a period of time.

• Journal of Electrical Engineering and Technology
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• v.7 no.4
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• pp.615-625
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• 2012

GPS attitude outputs or carrier phase observables can be effectively utilized to compensate the attitude error of the strapdown inertial navigation system. However, when the integer ambiguity is not correctly resolved and/or a cycle slip occurs, an erroneous GPS output can be obtained. If the erroneous GPS output is applied to the attitude determination GPS/INS (ADGPS/INS) integrated navigation system, the performance of the system can be degraded. This paper proposes an ADGPS/INS integration system using the triple difference carrier phase observables. The proposed integration system contains a cycle slip detection algorithm, in which the inertial information is combined. Computer simulations and flight test were performed to verify effectiveness of the proposed navigation system. Results show that the proposed system gives an accurate and reliable navigation solution even when the integer ambiguity is not correctly resolved and the cycle slip occurs.