After eliminating the gravimetric tides, linear drift and atmospheric mass attractions from data which were obtained by a superconducting gravity meter installed at Kyoto, Japan, residuals obtained were compared with estimated elastic effects using the atmospheric pressure distribution within an angular distance of 20°and a load Green's function. The residuals were in considerably good agreement with the estimated elastic effects except for some discrepancies of short periods. The observed elastic effects took about a middle value between elastic effects estimated for two extreme cases of the earth whose ocean bottom responded perfectly to the atmospheric pressure and of the earth whose ocean bottom did not respond to the atmospheric pressure at all. This result may indicate the presence of non-zero response of the ocean to the atmospheric pressure, the deviation of structure beneath the observation station from the mean earth's structural model, the influence of change in underground water levels, the truncated errors of integration and so on.

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Tidal gravity observations were made at Syowa and Asuka Stations, Antarctica, during wintering of the 28th Japanese Antarctic Research Expedition. LaCoste & Romberg type G gravity meters with electrostatic feedback amplifiers were used. The feedback voltage outputs were recorded every 30 minutes for both stations. The data with stable drift were selected and calibrated to tidal gravity variation. The number of selected data is 2976 from April 1 to June 1, 1987 for Syowa Station, and is 8656 from June 3 to November 30, 1987 for Asuka Station. The obtained tidal gravity data were analyzed by using the 'BAYTAP-G' program and oceanic tidal loading effects were corrected for by using the 'GOTIC' program. The a factors which are corrected for oceanic tidal loading effects distribute from 1.130 (K1) to 1.250 (M2) for Syowa Station, and from 1.134 (P1) to 1.330 (K2) for Asuka Station. For diurnal tides, there is no significant difference between the observed o factors and the theoretical values predicted by the Water's formulas. For semi-diurnal tides, how-ever, the observed a factors at both stations are larger than the Water's predictions by 10%-14%. The 8 factors at Asuka Station on the ice sheet (about 1, 000 m thick) are generally larger than those at Syowa Station on the basement rock of the East Ongul Island in Lutzow-Holm Bay. Since shorter period constituents (semi-diurnal tides), which reflect shallower crustal structures, deviated from the theoretical 8 factors to more positive values as compared with longer period constituents (diurnal tides), easily deformable ice sheet may have played an important role in the observed large 8 factors of semi-diurnal tides in the Antarctic region. The larger admittance of gravity change for atmospheric pressure at Asuka Station (-0.27 Fugal/mb) than that in mid-latitude observations (-0.35--0.37 Fugal/mb) may also be explained by easy loading deformation of the ice sheet by air mass for an extent of 30 km covering the site. However, detailed examination of the earth models including surface ice layers and comparison of the a factors for the fortnightly and ter-diurnal constituents with those for the diurnal and semi-diurnal constituents have to be made for accurate interpretation of the frequency dependence of the 8 factors in the Antarctic region.

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A GPS orbit determination software system called MSOP (Mufti-Satellite Orbit Processor) has been developed. This software uses pseudorange data to determine accurate orbits for the GPS satellite constellation. The paper describes some of the methods and strategies specific to precise orbit determination of GPS satellites with special emphasis on the force modeling for solar radiation pressure and y-bias. The orbit accuracy is evaluated from analysis of P-code pseudorange data collected by the Cooperative International GPS Network (CIGNET). This evaluation is based primarily on the direct comparison with the precise ephemerides generated at the Naval Surface Warfare Center (NSWC). Methods leading to orbit accuracy at better than 0.5 ppm level have been demonstrated.

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Loci of amplitudes of the earth tidal strains for the azimuth at Osakayama, Kishu and Suhara are studied analytically. Then elasticity and anisotropicc of the crust around these observatories are evaluated. The almost loci of the amplitude of the tidal strains in these observations are Cassinian curves which are two leaves' type. Few loci of them are four leaves' type, but their third and fourth leaves are very little. The loci of the direct effects which are calculated by assuming that Love's and Shida's numbers are 0.612 and 0.083, respectively are also two leaves' type. But, those of the load tidal strains are always four leaves' type. So, we may estimate the effect of the load tide in these observatories are not so large as those of the direct effect. Sum of the direct effect and the load tide which is calculated by use of selected elastic function of λ+μ are calculated to approximate the observed value. Then, the anisotropic deflections of the azimuths of the maximum tidal strains are obtainded as within the range of -7° and 12° in these observations. According to the analysi^, the type of the locus of the observed tidal strain for the azimuth is anomalous at Suhara on the south margin of the Median Tectonic Line. And this anomaly may be interpreated by the mechanism which the hydrostatic pressure on the ground-water just under the observatory caused by the change of the pressuer in the sea water due to the oceanic tide.

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The Geographical Survey Institute (OS!) is responsible for the national fundamental survey which has been carried out for the past century as the basis for mapping and engineering works. Main purposes of the fundamental survey are, at present, to get information for the prediction of earthquakes, by resurveying control points and to establish control points for the area where large scale mapping or cadastral survey is planned. The geodetic fundamental survey comprises a number of surveys; precise horizontal geodetic survey, levelling and astronomical observation.

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