Journal of the Geodetic Society of Japan
Online ISSN : 2185-517X
Print ISSN : 0038-0830
ISSN-L : 0038-0830
Volume 42, Issue 3
Displaying 1-4 of 4 articles from this issue
  • Tadahiro Sato, Kazuo Shibuya, Kazunari Nawa, Koji Matsumoto, Yoshiaki ...
    1996 Volume 42 Issue 3 Pages 145-153
    Published: December 25, 1996
    Released on J-STAGE: July 05, 2011
    JOURNAL FREE ACCESS
    Based on the tidal analysis using the 2-year data obtained from a superconducting gravimeter at Syowa Station, Antarctica (69.4°S, 39.6°E), and on the computations for the ocean tide effects using a new global ocean tide model by Matsumoto et al. (1995), we examined the tidal factors (8 factors) for the diurnal and semidiurnal tides at Syowa Station. As the a factors corrected for the ocean tide effects, we obtained the values of 1.144, 1.127, 1.157 and 1.111 for O1, K1, M2, and S2 waves, respectively. The discrepancies between the observation and Wahr's (1981) theory are at 0.5% for the diurnal tides and about 2% for the semidiurnal tides. Tudging from the consistency among the threeTadahiro Sato, Kazuo Shibuya, Kazunari Nawa, Koji Matsumoto and Yoshiaki Tamura observation results obtained by the three different gravimeters (Ogawa et al., 1991; Kanao and Sato, 1995; this study), and from the results for the computations of the ocean tide effects, it is highly probable that the large discrepancy exceeding 10% in the 8 factors for the semidiurnal tides at Syowa Station, which has been pointed out Ogawa et al. (1991), is mainly caused by their inaccurate estimation of the ocean tide effects.
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  • Tadanao O'ishi, Yoshimasa Sakurai, Katuo Seta, Ichiro Fujima, Tokuyuki ...
    1996 Volume 42 Issue 3 Pages 155-166
    Published: December 25, 1996
    Released on J-STAGE: September 07, 2010
    JOURNAL FREE ACCESS
    Twelve years observation of strain changes of a concrete tunnel in the soil wascarried out using a laser extensometer at Tsukuba, in the eastern part of Japan. Theterm is from 1980 to 1992. A dominant component of the strain changes is an annualchange and its amplitude reaches to 8×10-6. Linear trends were also observed. Irregular and rapid changes were observed. A model of strain change for the effect of outdoortemperature was constructed empirically using observed strains, out door temperature and temperature on the floor of the tunnel during 1986-1992. By eliminating cornponents caused byoutdoor temperature change, it becomes more simple to recognizestrain changes of the tunnel. Linear trend of the tunnel strain looks like changedafter 1984. From 1988 to 1989 a big strain change reaching 8×10-6 was observed.
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  • Shigekazu Kusumoto, Yoichi Fukuda, Shuzo Takemoto, Yuki Yusa
    1996 Volume 42 Issue 3 Pages 167-181
    Published: December 25, 1996
    Released on J-STAGE: July 05, 2011
    JOURNAL FREE ACCESS
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  • Ryuichi Ichikawa, Minoru Kasahara, Nobutaka Mannoji, Isao Naito
    1996 Volume 42 Issue 3 Pages 183-204
    Published: December 25, 1996
    Released on J-STAGE: March 01, 2011
    JOURNAL FREE ACCESS
    We evaluate positioning errors due to atmospheric excess path delay. These are calculated using the 10-km spectral model data (the l0-km data) provided by the Japan Meteorological Agency (JMA), considering two GPS satellite constellations within about 2 hours. The first has high elevation satellites (case A) and the other has low elevation satellites (case B). We compare the errors with those calculated using a spherically symmetric atmosphere. The difference between both errors indicates the effect of azimuthal asymmetry of the atmosphere. In this calculation, wet, hydrostatic, and total delay cases are evaluated. The magnitude of positioning errors due to wet delay from the three-dimensional atmosphere generally shows baseline length dependency for both single and double differences. When the baseline ranges 500 km in the direction of themaximum horizontal gradient of water vapor, the horizontal positioning errors reach 40 cm in case A and 50 cm in case B, while the vertical one reaches 30 cm in case A and 15 cm in case B. The magnitude of the errors also increases as the difference in the altitude between the two sites increases. In addition, the directions of the horizontal error vectors heavily depend on the azimuth of the lowest elevation satellite. The horizontal errors due to the azimuthal asymmetry of atmospheric excess path delay are evaluated as follows; (1) errors due to wet delay range from 0.5 to 4 cm, (2) errors due to hydrostatic delay are up to 1 cm, and (3) errors due to total delay range from 0.5 to 5 cm. The maximum horizontal errors are detected on the baseline azimuths which are consistent with the maximum horizontal gradient of water vapor and/or temperature. For all cases the vertical errors are generally less than 1 cm. These results imply that realistic, three-dimensional atmospheric data is required to attain subcentimeter accuracy in space geodetic techniques considering the azimuthal asymmetry of the atmosphere. The use of numerical prediction data is the most realistic and efficient method for this purpose. In addition, we expect that this method will also contribute to improving the numerical prediction model in the meso scale using interaction with GPS meteorology.
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