Journal of the Geodetic Society of Japan
Online ISSN : 2185-517X
Print ISSN : 0038-0830
ISSN-L : 0038-0830
Volume 15, Issue 1
Displaying 1-7 of 7 articles from this issue
  • Ichiro NAKAGAWA
    1969 Volume 15 Issue 1 Pages 2-5
    Published: November 30, 1969
    Released on J-STAGE: September 07, 2010
    JOURNAL FREE ACCESS
    Change of gravity with time is generally divided into two branches. One is a periodic variation and the other non-periodic. The periodic variation of gravity is phenomena caused by the tide-generating forces due mainly to the sun and the moon and caused also by other origins with periodicities, and its variation is regular. The non-periodic change of gravity, if existing, is regarded to be related with rapid or gradual change of gravity caused by the change of state or motion of the ground material, the fluctuation of rotation speed of the earth, the crustal movement and the like. In the present paper, there are some comments about observations of the time change of gravity made by means of gravimeters. Method of calibration for the gravimeters and that of data treatment are also discussed briefly.
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  • Wroking Group for Comparing the Gravimeters in Japan
    1969 Volume 15 Issue 1 Pages 6-8
    Published: November 30, 1969
    Released on J-STAGE: September 07, 2010
    JOURNAL FREE ACCESS
    Simultaneous gravimetric field survey was carried out after the continuous recording of earth tides, for the purpose of calibrating the scale constants of Askania gravimeters and LaCoste & Romberg gravimeters, and comparing the responsibilities of them to the large gravity change and meteorological change. Eight gravimeters were taken part in the survey. Four Askania gravimeters (Nr. 105, Nr. 111, Nr. 193, Nr. 197) and two L & R gravimeters (G 29, G 34) were the same one that used for the tidal observation, and another two L & R gravimeters (G 3, G 31) were merely jointed in this survey. Calibration line of about 200 kilometers length was established to the north direction from Mizusawa-its end point was Hachinohe-and three intermediate stations were provided on the line. The gravimetric return survey on the calibration line was completedin a day on Nov ember 20, 1968. The data were calculated by the same method, and discussion was made by comparing the discrepancies between the result of G 34 and that of each gravimeter.
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  • Hirokazu TAJIMA
    1969 Volume 15 Issue 1 Pages 9-13
    Published: November 30, 1969
    Released on J-STAGE: September 07, 2010
    JOURNAL FREE ACCESS
    Concerning the gravimetric field survey with gravimeter of helical spring type (mainly for a LaCoste and Romberg gravimeter of geodetic type), drifts and calibrated scale constant of the gravimeter which seem to be affected to the accuracy of survey are discussed in detail. Mechanical, thermal and other shocks to the gravimeter should be avoided, because such shocks during the field survey usually result in poor results. Stability of the LaCoste and Romberg gravimeter of geodetic type used is rather good during the whole period of the survey, and it is able to determine the scale constant of the gravimeter with an accuracy of 1/1000 or better.
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  • Minoru TAZIMA
    1969 Volume 15 Issue 1 Pages 14-19
    Published: November 30, 1969
    Released on J-STAGE: September 07, 2010
    JOURNAL FREE ACCESS
    Recently, there has been a growing possibility of the use of gravity survey to the research of crustal movement for the purpose of earthquake prediction, because of its speedy operation and the improved accuracy. In this occasion, discussions are made concerning the particular notices in the field survey by means of LaCoste gravity-meter of geodetic type, several error sources and examination of the survey results conducted by the Geographical Survey Institute.
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  • Naomi FUJITA
    1969 Volume 15 Issue 1 Pages 20-24
    Published: November 30, 1969
    Released on J-STAGE: July 05, 2011
    JOURNAL FREE ACCESS
    The equations of theoretical closing error in levelling circuit due to the non-parallelism of geopotential surfaces have been proposed.
    These equations are proved to be equivalent in principle as follows:
    ΔΣΔg-gim/gdhi=-1/gΔΣΔ(gimim)dhi-1/gΔΣΔγimdhi+ΔΣΔdhi-1/gΔΣΔγimdhi≈1/gΔΣΔ(γ0i+1/20i-1/2)hi-ΔΣΔdhi
    ∴ΔΣΔg-gim/gdhi≈-1/gΔΣΔ(gimim)dhi+1/gΔΣΔ(γ0i+1/20i-1/2)hi
    where dhi = hi-hi-1
    hi : measurement height at the point i in levelling circuit
    gi : gravity at i
    gim : mean of gravity values in the interval [i-1, i]
    g : mean of gravity values in the levelling circuit
    γi : standard gravity at i
    γi0: standard gravity on the reference ellipsoid below i
    γim : mean of standard gravity values in the interval [i-1, i]
    Let dhi be the sum of the true difference of height dhi0 and the observation error δχi dhi=dhi0 +δχi. Under suitable conditions,
    ΔΣΔg-gim/gdhi=ΔΣΔdhi-1/gΔΣΔgimdhi
    =ΔΣΔ(dhi0+δχi)-1/gΔΣΔgim+δχi∴∴1/gΔΣΔgimδχi (∴ΔΣΔgimdhi0=0)
    ≈ΔΣΔ(dhi0+δχi)-ΔΣΔδχi
    ΔΣΔdhi0
    The physical meaning of ΔΣΔg-gim/gdhi is that the theoretical value ΔΣΔdhi0 can be obtained by separating the observation error ΔΣΔδχi from the observation value ΔΣΔdhi using the gravity values in the levelling circuit.The theoretical closing error is defined as the simplest form,
    T.C.E≡ΔΣΔdhi0≈Σg-gim/gdhi .
    Here it is to be noticed that the equation is approximately derived from the definition mentioned above.
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  • Tetsuro HAYASHI
    1969 Volume 15 Issue 1 Pages 25-30
    Published: November 30, 1969
    Released on J-STAGE: September 07, 2010
    JOURNAL FREE ACCESS
    In this paper, the writer investigates the accuracy of the levellings of high precision which have been carried out by the Geographical Survey Institute in Japan. The main resulted conclusions are as follows: (1) The standard deviations of the measured values resulted by the levelling surveys are ±2030 mm/km. The misclosures in one third level-circuits of all excess the limitation of misclosure, 2.0 mmVL (km), where L is the length of a circuit. Almost of all the misclosures of level-circuits whose lengths are shorter than 100 kilometers keep within the limitation of misclosure, while one-half that of which the lengths are longer than 600 kilometers goes over the limitation. (2) The gravity corrections to the closures of level-circuits are shown in Fig. 3 and Table V. The difference between the closure in level-circuit corrected the normal orthometric correction by the normal gravity value and that corrected the gravity correction by the measured gravity value is 34.2 millimeters in maximum. (3) The standard deviations of elevations of the bench marks, as shown in Figs. 4(a) and 4(b), are 12 cm in Kanto district, 34 cm in Chugoku and Tohoku districts, and 46 cm in Kyushu and Hokkaido districts. Roughly speaking, the error of the adjusted elevation of a bench mark increases in proportion to the distance of the levelling route from the datum in Tokyo to its bench mark.
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  • 1969 Volume 15 Issue 1 Pages 31-40
    Published: November 30, 1969
    Released on J-STAGE: September 07, 2010
    JOURNAL FREE ACCESS
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