Journal of the Geodetic Society of Japan

We have some advantages in GPS survey to develop network adjustment with aid of geocentric rectangular coordinates, because not only some results of survey are given directly based on WGS-84 geocentric rectangular coordinate but also theoretical considerations are much simplified. We developed weighted free adjustment of GPS three-dimensional network with observed baseline vectors or observed spatial distances as well as some formula that are required to discuss the vertical and horizontal displa cement of GPS stations from the results of rectangular coordinates adjustment. Constraint equation of the type CX=0 is generally applied for solution of rank deficient normal equation, where C is constraint matrix and X is estimated parameter matrix. This constraint equation is further extended to be CMX=0, where M is interpreted to be a weight matrix to X. We can estimate M with the conventional free adjustment or with some geophysical informations. The solution with constraint of this type can also include so called classical free adjustment such as the case with one fixed station and one fixed direction or with two fixed stations and so on as some special cases.

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The first field observation using SONY GTT-4000, a GPS interferometer, was done in the south Kanto EDM network of the Earthquake Research Institute. Three receivers-single frequency version- were deployed at three sites that composes a triangle withside distances of about 8, 12 and 14 km. The present paper briefly introduces the receiver and compare the estimated distances with the EDM observations. The results by GTT-4000 shows better than 2 ppm consistency with EDM. Misclosures of the triangle which was obtained by the relative coordinate estimates were smaller than 1 ppm.

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The wet component of excess path delays in the troposphere were studied with regards to geodetic baseline measurements using the Global Positioning Systems (GPS). The wet delays at the zenith obtained by the software (SONAP, provided by Western Geophysical Division, Western Atlas International, Inc.) for the simultaneous estimation of the geodetic parameters of stations in the highlands were found to be significantly larger than those for the sites near sea level. The apparent discrepancy could not be resolved in this investigation and further study is needed. We evaluated the wet delays at the zenith τ_z^w taking into account the characteristics of distributions of meteorological parameters near the surface layer over central Japan. A modified formula for τ_z^w to that of Saastamoinen (1972) was derived as, τ_z^w=191e1*/T1* (cm), where e1 =1.3e1, with e1 being the water vapor pressure (mb) on the ground surface and T1 being the extrapolated temperature (K) on the ground surface from the constant-lapse rate distribution prevailing in the dominant region of the troposphere. The procedures to infer the wet-term excess path delays at the zenith on the highlands are proposed, and the resultant correction coefficient versus the altitude is presented herein.

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