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Spatial Decorrelation of SBAS Satellite Error Corrections in the Korean Peninsular
Jaegyu Jang,Hyoungmin So,Kihoon Lee,Jun-Pyo Park 한국항공우주학회 2016 International Journal of Aeronautical and Space Sc Vol.17 No.1
The characteristics of the SBAS satellite orbit and clock corrections are highly affected by the narrow network size in the Korean peninsula, which is expected to have an important role in the future dual frequency SBAS. The correlation between satellite corrections can be analyzed in terms of the spatial decorrelation effect which should be analyzed to keep the service area as wide as possible. In this paper, the characteristics of satellite error corrections for the potential Korean dual frequency SBAS were analyzed, and an optimal filter design approach is proposed to maximize the service area.
Jang, Jaegyu,Kee, Changdon Cambridge University Press 2009 The Journal of navigation Vol.62 No.3
<P>This paper describes the verification of a real-time attitude determination algorithm during GPS attitude receiver hardware development. The GPS attitude receiver of 24 channels had been already developed in Surrey University. However 24 channels were not enough for practical usage. For this reason, a 48-channel attitude receiver with 12 channels for each antenna has been developed. To estimate attitude in real time, precise relative positions of the GPS antenna array have to be determined as rapidly as possible. However, the calculation load based on the conventional algorithm is too burdensome to perform using the RISC microprocessor. Therefore, in this paper, the cycle ambiguities of each base vector are resolved using SNUGLAD (Seoul Nat Univ GNSS Lab Attitude Determination), the design focus of which is to allow the receiver to estimate the 10 Hz onboard solutions. To keep precise solutions continuously, after ambiguity removal, cycle slip must be detected or isolated. Otherwise, the receiver would output erroneous solutions after a short signal blockage or fading of the GPS signal. To prevent this, we defined the cycle slip detection and repair scheme using a standard extended Kalman filter, which can detect and repair cycle slip within one cycle. As a result, this paper shows that time synchronized measurement with good quality and a reliable solution can be provided by the hardware developed with inexpensive chipsets and that this may be a possible cost efficient sensor for UAV or microsatellites.</P>
Jaegyu Jang,Hyoungmin So,Kihoon Lee,Jun-Pyo Park IET 2017 IET radar, sonar & navigation Vol.11 No.4
<P>This study verifies the performance of the ionosphere-free L1 pseudorange for dual-frequency space-based augmentation systems (SBAS) users by both of theoretical analysis and experiments with actual GPS data. Although the dual-frequency pseudorange from ionosphere-free linear combinations is commonly used as a standard method, the ionosphere-free L1 range based on the weighted Hatch filter has advantages in terms of the amplification factor caused by a dual-frequency combination and filter weights optimised by the least-squares method. For the experimental analysis, RINEX data were collected from five National Geographic Information Institute reference stations on the Korean peninsula and used to generate an SBAS correction message following international SBAS specifications. The experimental results show that using the proposed method results in a 29% improvement in the range domain compared with the use of a traditional ionosphere-free linear combination filter. In the position domain, the proposed method shows a horizontal accuracy improvement of 16% after the application of post-processed SBAS orbit/clock corrections w.r.t. the traditional filter. Finally, this study also demonstrates that the accuracy of dual-frequency users can surpass than that of single-frequency SBAS users only if corrections are estimated with ionospheric delay-free measurements in the master station as well.</P>
Spatial Decorrelation of SBAS Satellite Error Corrections in the Korean Peninsular
Jang, Jaegyu,So, Hyoungmin,Lee, Kihoon,Park, Jun-Pyo The Korean Society for Aeronautical and Space Scie 2016 International Journal of Aeronautical and Space Sc Vol.17 No.1
The characteristics of the SBAS satellite orbit and clock corrections are highly affected by the narrow network size in the Korean peninsula, which is expected to have an important role in the future dual frequency SBAS. The correlation between satellite corrections can be analyzed in terms of the spatial decorrelation effect which should be analyzed to keep the service area as wide as possible. In this paper, the characteristics of satellite error corrections for the potential Korean dual frequency SBAS were analyzed, and an optimal filter design approach is proposed to maximize the service area.
Integer Ambiguity Search Technique Using Separated Gaussian Variables
Doyoon Kim,Jaegyu Jang,Changdon Kee 한국항공우주학회 2004 International Journal of Aeronautical and Space Sc Vol.5 No.2
Real-Time Kinematic GPS positioning is widely used for many applications. Resolving ambiguities is the key to precise positioning. Integer ambiguity resolution is the process of resolving the unknown cycle ambiguities of double difference carrier phase data as integers. Two important issues of resolving are efficiency and reliability. In the conventional search techniques, we generally used chi -square random variables for decision variables. Mathematically, a chi-square random variable is the sum of mutually independent, squared zero-mean unit-variance normal (Gaussian) random variables. With this base knowledge, we can separate decision variables to several normal random variables. We showed it with related equations and conceptual diagrams. With this separation, we can improve the computational efficiency of the process without losing the needed performance. If. we average separated normal random variables sequentially, averaged values are also normal random variables. So we can use them as decision variables, which prevent from a sudden increase of some decision variable. With the method using averaged decision values, we can get the solution more quickly and more reliably. To verify the performance of our proposed algorithm, we conducted simulations. We used some visual diagrams that are useful for intuitional approach. We analyzed the performance of the proposed algorithm and compared it to the conventional methods.