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Volume 34 (1988)
- Issue 3-4 Pages 157-
- Issue 2 Pages 97-
- Issue 1 Pages 1-
Volume 34, Issue 3-4
Displaying 1-8 of 8 articles from this issue
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Yutaka YABUTA, Nobuyuki KAWANO, Ichiro NAKAGAWA1988 Volume 34 Issue 3-4 Pages 157-176
Published: December 25, 1988
Released on J-STAGE: July 05, 2011
JOURNAL FREE ACCESSA simple computer program to process precise relative positioning data by means of Global Positioning System (GPS) was made and tested applying to both simulation and actual data. Simulation data were made from theoretically calculated phases by adding random numbers as measurement errors, under an actual configuration of satellites. In this case, errors of the solution became several times larger than those expected from the measurement errors assumed. It is concluded that observation equations are ill-condi-tioned because the present configuration of satellites is poor. By the results from various experiments, an extension of measurement duration is expected to be most effective for obtaining a precise geodetic solution. On the other hand, actual data were obtained by means of PRESTAR, a GPS receiver. It was found that the data included a drift-like variation of a clock difference, and this required adding a new unknown parameter. However, it was almost impossible to simultaneously estimate all the unknown parameters. An expected result was obtained by reducing the number of parameters to be estimated simultaneously, though there still remain systematic errors. Since these errors are considered due to errors of the clock variation from its linear approximation, a measurement duration should be as short as possible for the variation to become linear. From the results obtained by both simulation and actual data, we propose the following measurement method for more precise relative positioning. Several measurements should be repeated at fit intervals, while each measurement should be as short as possible. By this procedure, all the unknown parameters will simultaneously be estimated.View full abstractDownload PDF (7413K) -
Hideo HANADA, Tsuneya TSUBOKAWA, Seiitsu TSURUTA, Taizou YOSHINO1988 Volume 34 Issue 3-4 Pages 177-184
Published: December 25, 1988
Released on J-STAGE: September 07, 2010
JOURNAL FREE ACCESSCollocative measurements by an absolute gravimeter have been carried out at Kashima Space Research Center, Communications Research Laboratory, one of the VLBI IRIS-P Networks, from January 18 to 23, 1988. The observation site is located near a manu facturing district and the ground vibrations caused by human activities such as traffic noise extremely affected the measurements . The maximum acceleration due to the traffic amounted to more than 2X10-4 ms-2 (20 mGal). The effects of the vibrations caused by the operation of the 26 m diameter antenna, on the other hand, were relatively small compared to the large traffic noise, so we could not detect them at the point about 30 m distant from the antenna. The uncertainty in the results from 194 drops is about 3X10-7 ms-2 (30μGal), which is almost ten times larger than that obtained at Esashi. The main cause of the error can be considered as the traffic vibrations and we can correct their effects with the accuracy better than one percent.View full abstractDownload PDF (5422K) -
Tsuneji RIKITAKE1988 Volume 34 Issue 3-4 Pages 185-195
Published: December 25, 1988
Released on J-STAGE: September 07, 2010
JOURNAL FREE ACCESSFor the purpose of accounting for the fact that very few precursors are observed for relatively deep earthquakes, crustal strains and tilts at the ground surface are estimated assuming a simple force at depths. As for the source, a spherical cavity subjected to an internal pressure and a vertical unit fault slipping in the horizontal direction are assumed. It turns out that ground strains and tilts at the surface change proportionally to the inverse of the 3rd or 4th power of the origin depth immediately above the source. This suggests that the magnitude of strain and tilt, which might be associated with a precursory event in the source region, become extremely small for a deep origin. It is therefore not surprising that the deeper the hypocenter is, the more difficult becomes the detection of a precursor.View full abstractDownload PDF (792K) -
Izuo OZAWA1988 Volume 34 Issue 3-4 Pages 197-204
Published: December 25, 1988
Released on J-STAGE: March 01, 2011
JOURNAL FREE ACCESSRecently, reliable values of constants, h and l on the earth tide have been obtained by means of both of theoretical evaluations and observations of the tidal strains. So, it is very significant to make the schematic expressions of distributions of the tidal displacements. The author makes some schematic diagrams of distributions of the tidal displacements. The illustrations are diagrams of horizontal component of the tidal displacements and of signs of the vertical component of the tidal displacements on plane maps of the earth's surface. The other illustrations are the distributions of projections of the tidal displacements on the meridional and the equatorial planes. These illustrations give concise account of characteristics of these pattern of distributions.View full abstractDownload PDF (615K) -
Yoshiko KOTAKE, Yukio HAGIWARA1988 Volume 34 Issue 3-4 Pages 205-217
Published: December 25, 1988
Released on J-STAGE: September 07, 2010
JOURNAL FREE ACCESSA trial on line extraction from the digital terrain model (DTM) is performed by using a method which is generally used for processing digital pictures. It consists of the following steps; (1) extracting feature points like edges and bounderies from a grey picture by applying the Laplacian operator of 4x4 elements, (2) reforming a binary picture whose points have the gradation greater than a certain threshold value, (3) reforming a line pattern by the thinning algorithm with properties of connected components, (4) detecting straight lines in a digitized image by the Hough transformation. This method replaces an original problem of finding collinear points in picture space by a mathematically equivalent problem of finding concurrent lines in parameter space . Most of the lineament spicked up from DTM of the Iida district and from Bouguer anomaly in the Suwa basin show relatively good agreements with the distribution of active faults. In conclusion, the Hough transformation can detect lineaments efficiently from a complex map.View full abstractDownload PDF (2988K) -
Naosuke SEKIGUCHI1988 Volume 34 Issue 3-4 Pages 219-220
Published: December 25, 1988
Released on J-STAGE: September 07, 2010
JOURNAL FREE ACCESSThe recalculation of the so-called "Microscopic Chandlerian Period", proposed in the previous papers [1], [2], was performed using the updated 6 year data of ERP. In order to avoid the effect of smoothing, 10 days differences of the polar coordinates were replaced by the 5 days differences. The recent improvement in the observastional accuracies performed by the modern technics, enables this replacement. The result was found to be 402.4 days.View full abstractDownload PDF (216K) -
Yutaka YABUTA, Ichiro NAKAGAWA, Kunio FUJIMORI, Satoshi FUJIWARA, Kaju ...1988 Volume 34 Issue 3-4 Pages 221-222
Published: December 25, 1988
Released on J-STAGE: September 07, 2010
JOURNAL FREE ACCESSThe repeatability of GPS measurements by employing WM101 was investigated as one of methods to evaluate the accuracy of the solutions. The dispersion of daily solutions became several tens of centimeters which correspond to several tens of ppm. However, some of the solutions met each other with the dispersion of several ppm.View full abstractDownload PDF (233K) -
Teruyuki KATO1988 Volume 34 Issue 3-4 Pages 223-225
Published: December 25, 1988
Released on J-STAGE: July 05, 2011
JOURNAL FREE ACCESSDownload PDF (288K)
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