• Journal of Astronomy and Space Sciences
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• 제33권1호
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• pp.45-54
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• 2016

This study developed an approach for improving Carrier-phase Differential Global Positioning System (CDGPS) based realtime satellite relative navigation by applying laser baseline measurement data. The robustness against the space operational environment was considered, and a Synthetic Wavelength Interferometer (SWI) algorithm based on a femtosecond laser measurement model was developed. The phase differences between two laser wavelengths were combined to measure precise distance. Generated laser data were used to improve estimation accuracy for the float ambiguity of CDGPS data. Relative navigation simulations in real-time were performed using the extended Kalman filter algorithm. The GPS and laser-combined relative navigation accuracy was compared with GPS-only relative navigation solutions to determine the impact of laser data on relative navigation. In numerical simulations, the success rate of integer ambiguity resolution increased when laser data was added to GPS data. The relative navigational errors also improved five-fold and two-fold, relative to the GPS-only error, for 250 m and 5 km initial relative distances, respectively. The methodology developed in this study is suitable for application to future satellite formation-flying missions.

• Journal of Positioning, Navigation, and Timing
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• 제4권1호
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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.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2000년도 춘계학술대회논문집
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• pp.1303-1310
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• 2000

GPS carrier phase is supposed to provide the tool for the most precise 3 dimensional positioning information. The FAST, an OTF technique, has been developed by the GPS System Laboratory of Konkuk University, and has been shown several millimeter level accuracy in root-mean-square sense. This OTF's high precision positioning capability provides an adequate tool of low frequency vibration monitoring of large structures. In this paper, the possibility of vibration measurement of a cantilever beam using FAST has been tested, which is supposed to be extended to more practical applications. The results of the experiment have been compared with those by a strain gage and laser sensor.

• 한국측량학회:학술대회논문집
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• 한국측량학회 2004년도 춘계학술발표회논문집
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• pp.45-49
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• 2004

The Navstar Global Positioning System(GPS) is an advanced navigation satelite system for determination of position, velocity and time. It can provide three-dimensional positioning on a global basis, independent of weather, 24 hours per day. Test results show that the carrier phase and pseudorange corrections are suitable for a kinematic GPS system. Using these corrections are more effective than using raw GPS data, since fewer bits are required for transmission Additionally, the number of computation required at the rover is reduced when corrections, rather than raw measurement are transmitted

• 제어로봇시스템학회논문지
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• 제5권1호
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• pp.62-68
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• 1999

The attitude of a vehicle can be precisely determined using GPS carrier phase measurements from more than two antennas attached to a vehicle and an efficient integer ambiguity resolution technique. Many methods utilizing the known baseline length as a constraint of independent elements of integer ambiguities are proposed to resolve integer ambiguity at real time. Three-dimensional search space is reduced to two-dimensional search space with this constraint. Thus the true integer ambiguity can be easily determined with less computational burden and fewer number of measurements. But there are still strong requirements for the real time integer ambiguity resolution, which uses single epoch measurement of long baseline. In this paper, a new constraint from the geometry of multiple baselines is derived. With this new constraint, two-dimensional search space is further reduced to one-dimensional search space. It makes possible to determine integer ambiguity with single epoch measurement. The proposed method is applied to real data to show its effectiveness.

• Journal of Positioning, Navigation, and Timing
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• 제4권4호
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• pp.195-203
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• 2015

In this study, the carrier acceleration-ramp-step test was applied to GPS carrier phase measurements, and the results were compared and analyzed. In the carrier acceleration-ramp-step test, the acceleration, ramp, and measurements are estimated using 10 consecutive carrier phase measurements for satellites observed at the same time based on the least square method. As for the characteristic of this test, if failure occurs in the measurement, the value jumps significantly compared to the previous result; but it judges that failure has occurred in all the satellites although failure has occurred in one satellite. Therefore, in this study, a method that eliminates a satellite with failure was suggested, and thresholds of the carrier acceleration, ramp, and step were suggested. The evaluation of the failure detection performance of carrier phase measurement using the suggested thresholds showed that failure could be detected when the carrier phase measurement changed abruptly by more than about 0.1 cycles.

• 한국항공우주학회지
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• 제33권3호
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• pp.65-70
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• 2005

잘못된 미지정수는 잘못된 위치값을 사용자에게 제공하여 자세결정에 큰 오차를 발생시킨다. 본 논문에서는 이동하는 항체에 4개 이상의 GPS 안테나를 고정시켜 정확한 자세결정을 수행할 때 다중경로를 추정하는 방법을 제안하였다. 4개 이상의 GPS 안테나에서 얻은 측정값이 같은 수신기 시계오차를 갖게 되면, 안테나 사이의 기하학적 관계를 이용하여 자세결정을 보다 효과적으로 수행할 수 있다. 안테나 사이의 거리를 반파장으로 만들어 미지정수 검색의 과정 없이 미지정수를 결정하고, GPS 반송파 측정값에 존재하는 다중경로 오차를 추정할 수 있다. 본 논문은 GPS 반송파 측정값의 다중경로 오차를 추정하는 알고리즘을 제시하고 수학적인 증명을 하였으며, 이 결과를 시뮬레이션을 통해 검증하였다.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2003년도 ICCAS
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• pp.2325-2330
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• 2003

GPS based orbit determination system for the KOMPSAT-2 has been developed. Two types of orbit determination software such as operational orbit determination and precise orbit determination are designed and implemented. GPS navigation solutions from on-board the satellite are used for the operational orbit determination and raw measurements data such as C/A code pseudo-range and L1 carrier phase for the precise orbit determination. Operational concept, architectural design, software implementation, and performance test are described.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2001년도 ICCAS
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• pp.141.5-141
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• 2001

An attitude GPS receiver with 3 antennas obtains 3-dimensional attitude using GPS carrier phase measurement INS obtains the 3 dimensional navigation solution for IMU consisting of accelerometers and gyro. Ground-alignment process for the low -cost INS cannot be performed well due to the large sensor noise. Using the standard GPS receiver, however, continuous in-flight alignment for the INS becomes possible, and consequently, the errors in IMU sensors and navigation solution can be compensated. Especially with attitude measurement from the attitude GPS receiver, the compensation of errors in gyroscope and attitude would be done respite of the vehicle´s dynamics and their error covariance would be reduced. This paper presents ...

• 제어로봇시스템학회논문지
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• 제11권7호
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• pp.644-650
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• 2005

The expected positioning accuracies of civil users utilizing modernized GPS and Galileo are derived using the error analysis in this paper. Since, in general, the performance of DLL, PLL and FLL is proportional to chip lengths and wavelengths, the positioning accuracies from various measurements of modernized GPS and Galileo are derived as function of chip length and wavelength. These results are compared with that from GPS Ll measurement. In absolute positioning, compared to GPS C/A code only case, more than 17 times performance improvement is expected when all civil code signals of modernized GPS and Galileo (L1, L2, L5, E1, E5A and E5B) are used. In relative positioning, compared to GPS L1 carrier phase only case, more than 2 times performance improvement is expected when all civil signals of modernized GPS and Calileo are used. Furthermore, the relationship between GDOP and RGDOP in single frequency case is expanded to general case where multiple frequencies and both code and carrier phase measurements are used.