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Author: search.filters.author.Tongkasem, NapatSubject: search.filters.subject.low geomagnetic latitude

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    Precise total electron content map monitoring in low latitude region
    (2022-01-01)
    Tongkasem, Napat
    ;
    Myint, Lin M.M.
    ;
    Supnithi, Pornchai
    The need for accurate Global Navigation Satellite System (GNSS) positioning is necessary for GNSS applications such as Real-Time Kinematic (RTK), Precise Point Positioning RTK (PPP-RTK), etc. The ionosphere delay, especially in low latitude region, is a main cause of positioning error. The usage of electron maps in GNSS applications can help with the first ionosphere correction. The Global Ionosphere Map (GIM) is a large-scale service for the Total Electron Content (TEC) with a resolution of 2.5 for latitude and 5 for longitude which may not be proper to high resolution GNSS applications in the small or regional regions. Over the low latitude region, we apply the local TEC from 4 stations which has similar longitude to observe the differential TEC. Then, we generate the precise grid TEC maps from 18 GNSS stations with different resolution of grid for observe the appropriate values. The results are shown that the resolution of 1.5 for latitude and 3 for longitude has RMS 1.58 of TECu compare with the local TEC value, while GIM has RMS of 2.11 TECu.
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    The disturbance effects on single frequency GPS positioning at low geomagnetic latitude stations in Thailand
    (2020-07-01)
    Tongkasem, Napat
    ;
    Myint, Lin M.M.
    ;
    Supnithi, Pornchai
    ;
    Komolmis, Tharadol
    ;
    Hozumi, Kornyanat
    The ASEAN IVO project currently supports the research related to GNSS and ionospheric data products for disaster prevention and aviation in low-latitude regions. In the positioning system, the atmosphere is the main medium along the propagation path that includes some ions, water vapor, and noise. These are the causes of the propagation delay time especially the ions in the ionosphere. At the present, there are many Global Positioning System (GPS) stations worldwide. Therefore, we can check the performances of the positioning system by using the positioning error calculation. In this work, the positioning errors are calculated from the 16 GPS stations at the low geomagnetic latitude region (Thailand) with the single frequency algorithm on a disturbance day. Then, we compute the 95-percentile and the maximum of the positioning errors. The results show approximately the difference of 95-percentile value 1.799 meters on the horizontal axis and 2.289 meters on the vertical axis and maximum positioning error can be up to 11.413 meters on the disturbed time on the disturbance day.