Journal of the Geodetic Society of Japan
Online ISSN : 2185-517X
Print ISSN : 0038-0830
ISSN-L : 0038-0830
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Volume 44, Issue 1
Displaying 1-5 of 5 articles from this issue
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  • On the Data Analysis of the Western Pacific Integrated Network of GPS (Part 1 )
    Yoshiko Kotake, Teruyuki Kato, Shigeru Nakao, Kazuro Hirahara, Masami ...
    1998 Volume 44 Issue 1 Pages 1-19
    Published: March 25, 1998
    Released on J-STAGE: July 05, 2011
    DOIhttps://doi.org/10.11366/sokuchi1954.44.1
    JOURNAL FREE ACCESS
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    In order to investigate crustal deformations and to help establish national geodetic datum of countries in the western Pacific region, a continuous GPS tracking network was designed in 1995. We have established 10 stations by November 1997. The network was named as Western Pacific Integrated Network of GPS (WING). In addition, more than 10 stations of International GPS Service for Geodynamics (IGS) have been established by other institutes in this region. Among these sites, data from Marcus, Guam, Chuuk, Palau, Manila, Ishigaki, Taipei, Shanghai, Taejeon, Vladivostok, Usuda and Lhasa were used for crustal deformation analyses in July 1995-October 1996 together with 6 IGS fiducial sites. A fiducial-free approach was employed to obtain the most accurate baseline estimates. To fix the estimated coordinates to the terrestrial reference frame, the Tsukuba IGS site was assumed to be moving about 2cm/yr westward relative to the stable Eurasian continent (Heki, 1996). We find that velocities of Marcus and Chuuk are in good agreement with a rigid plate motion model. On the other hand, Ishigaki and Guam seem to be moving trenchward, suggesting on-going back-arc openings. Stations in the eastern margin of the Asian continent such as Taejeon, Shanghai and Taipei are moving E-ESE relative to the stable Eurasian continent, due possibly to the collision between India and Asia.
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  • Mitigation of GPS Carrier Phase Multipath by Microwave Absorbing Material
    Takao Tabei, Kyoko Kobayashi
    1998 Volume 44 Issue 1 Pages 21-31
    Published: March 25, 1998
    Released on J-STAGE: September 07, 2010
    DOIhttps://doi.org/10.11366/sokuchi1954.44.21
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    For the realization of millimeter-precision positioning by the Global Positioning System (GPS), effective measures against carrier phase multipath resulting from reflection in the vicinity of receiver antenna were discussed through field experiment on a short 7.3-m baseline. It became clear that horizontal, flat reflector just below the antenna was the main source of multipath and produced a systematic variation of postfit phase residual with time. By covering the reflector with microwave-absorbing sheets with an area of 0.313m2, systematic variation of phase residual has been decreased. We manufactured microwave-absorbing hood for preventing the GPS signals arriving from below from being diffracted at the edge of the antenna groundplane. While attachment of hoods to two antennas certainly reduced multipath, they were not so effective as the sheets laid below the antenna. Distance and height difference between hood and antenna groundplane, as well as shape of the hood itself, must have critical effects, though their physical characteristics was not discussed in detail in this study. We performed satellite elevation cutoff test under various conditions changing attachment/demount of microwave-absorbing hood and sheet. When neither the hoods nor sheets were in place, estimates of vertical coordinates of the antenna were sensitive to the minimum elevation angle, showing apparent change of up to 4mm as the angle was changed from 5° to 30° . On the other hand, attachment of all hoods and sheets reduced apparent change of estimates within lmm. Thus, microwave-absorber is a simple but powerful tool to mitigate GPS carrier phase multipath and enhance total signal-to-noise ratio at the GPS antenna.
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  • A Walsh Gravity Analysis of the Seismogenetic Faulting Structure
    Yukio Hagiwara, Chizu Itota, Ryuichi Shichi
    1998 Volume 44 Issue 1 Pages 33-36
    Published: March 25, 1998
    Released on J-STAGE: September 07, 2010
    DOIhttps://doi.org/10.11366/sokuchi1954.44.33
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    We propose an analytic method using the Walsh function for extracting smallscale disturbances From the gravity anomaly map. Its applicability is proved actually in the gravity data analysis rearding the seismogenetic faulting of the 1984 Western Nagano Prefecture Earthquake .
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  • Short-Term Repeatability of GPS Measurements on the Short Baseline Using Single-Frequency Resolution
    Fumiaki Kimata, Akiko Yamada
    1998 Volume 44 Issue 1 Pages 37-41
    Published: March 25, 1998
    Released on J-STAGE: September 07, 2010
    DOIhttps://doi.org/10.11366/sokuchi1954.44.37
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    From the GPS data observed by doublefrequency receivers, baseline determinations by single-frequency and double-frequency resolutions are compared for the baseline with a length of 4.4 km over the seven days interval. Short-term repeatabilities of 1-2 mm in horizontal baseline determination by single-frequency resolutions are superior to that of ionosphere free by doblefrequency technology in all the three dimensions of baseline determinations.
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  • The 13th International Symposium on Earth Tides (Brussels)
    Shuzo Takemoto
    1998 Volume 44 Issue 1 Pages 43-47
    Published: March 25, 1998
    Released on J-STAGE: September 07, 2010
    DOIhttps://doi.org/10.11366/sokuchi1954.44.43
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