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Access type: UnknownAuthor: search.filters.author.Chiablaem, Athiwat

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    Study of GPS instrumental bias and TEC estimations from GPS stations in Thailand
    (2017-11-03)
    Chiablaem, Athiwat
    ;
    Phakphisut, Watid
    ;
    Supnithi, Pomchai
    The Total Electron Content (TEC) or satellite delay can be derived from the dual-frequency of Global Positioning System (GPS). The error of TEC accuracy suffers seriously from the GPS instrumental biases, including satellite bias and receiver bias. In this paper, we apply the singular value decomposition (SVD) to derive TEC, GPS satellite and receiver biases from the 11 GPS receiver stations in Thailand, which are operated by DPT. From the results, the daily satellite bias range between -8 ns and 10 ns. The estimated receiver bias varies from -5.03 ns to 1.88 ns. The biases in TEC are removed. The TEC estimation by SVD method is a good agreement level at each locations. The TEC of SVD estimation is compared with a TEC of general calculation by a GPS receiver from DPT9. The estimated TEC by SVD method at Bangkok area is used. The trend of both TEC are concurrence. Thus, the SVD method can be used to estimate the TEC, GPS satellite and receiver biases in Thailand area.
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    Estimation of the single GPS-receiver bias using the gradient descent algorithm
    (2016-09-06)
    Chiablaem, Athiwat
    ;
    Supnithi, Pornchai
    ;
    Klinngam, Somjai
    ;
    Panachart, Chaiwat
    ;
    Saekow, Apithep
    The ionospheric Total Electron Content (TEC) can be obtained from processing measurements of the dual-frequency Global Positioning System (GPS) receiver. The main sources of errors in the TEC calculation are satellite and receiver biases. In this paper, we apply the gradient descent algorithm on the receiver bias estimation. The TEC is derived from measurements at 12 dual-frequency GPS stations in Thailand. The criterion of receiver bias estimation is based on the minimum sum of the vertical TEC (VTEC) standard deviation method. The results show that the maximum receiver bias value is approximately 3.69 ns at UDON station, while the minimum value is -5.91 ns at SRTN station. The accuracy of the receiver biases from this algorithm is compared with the reference method. The maximum percentage deviation is about 7.5% at SRTN station. The percentage deviation of the minimum sum of the VTEC between the reference method and the proposed method from all stations are less than 0.05%. Thus, the proposed algorithm is a viable option to estimate the receiver bias.