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The history of geodesy can be traced back to Thales of Miletus (∼600 BC), who developed the concept of geometry, i.e. the measurement of the Earth. Eratosthenes (276–195 BC) recognized the Earth as a sphere and determined its radius. In the 18th century, Isaac Newton postulated an ellipsoidal figure due to the Earth's rotation, and the French Acade...
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... with triangulation results (see Fig. 2). Discussions on this method continued in Section V until more and more gravity observations became available. Heiskanen published in 1957 a global geoid using all available gravity data in a grid of 6679 geographic 1 • × 1 • blocks (Fig. 3). Discussions focussed on the applied methods, e.g. Stokes' integral, spherical harmonics, and least squares ...
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This paper studies the reconstitution of the International Geodetic and Geophysical Union after the First World War. Covering the period 1917–1922, it questions the historical signification of geodesy and its evolution from the local and particular point of view of the members of the Bureau des longitudes, the French “academy of astronomical sciences” which included, from its creation in 1795, prestigious mathematicians, Navy and Artillery officers, and distinguished precision instrument-makers. Taking as an archival sources the minutes of the Bureau des longitudes, and focusing on its small but very significant network of actors, my proposal is twofold: firstly, showing the strong involvement of its members into the administration of French sciences and technologies, and into the constitution of a renewed and selected post-war international geodetic community. Secondly, and more generally, relying on a specific and national context of actors and instruments, I want to encourage a more extensive and comprehensive study of post-war international geodesy.
Due to current situation in Kosova with the national geoid, which is still under development, utilization of global EGM's is more than necessary. In this research, multiband raster datasets with 1km spatial resolution of existing EGM 2008, 1996, and 1984 have been developed. Maximal and minimal differences between the models, range of extreme values of geoid heights in three geoid models, mean heights and other data calculations, are given in this paper. Calculation have been performed with online geoid calculator GeoidEval, in grid of 10893 points. Based on developed multiband raster model dataset and calculated differences between the models, three maps for the territory of Kosova were compiled. Main purpose of performed research analyses and developed GIS datasets for geoid heights, is free and open for usage by the geo community in Kosova, till the establishing of state gravimetrical network and model.
Abstract We developed a refined gravimetric geoid model for Japan on a 1 × 1.5 arc-minute (2 km) grid from a GOCE-based satellite-only global geopotential model and a regional gravity field model updated in this study. First, we have constructed a regional gravity field model for Japan using updated gravity datasets together with a residual terrain model: 323,431 land gravity data, 77,389 shipborne marine gravity data, and Sandwell’s v28.1 altimetry-derived global marine gravity model. Then, the geoid was determined with the gravity field model. The methodology for gravimetric geoid determination was based on the remove–compute–restore technique with Helmert’s second method of condensation of topography (Stokes–Helmert scheme). Here, the hybrid Meissl–Molodensky modified spheroidal Stokes kernel was employed to minimize the truncation error under an appropriate combination of different kinds of gravity data. In addition, a high-resolution GSI-DEM on a 0.4 × 0.4 arc-second (10 m) grid, together with the SRTM-DEM on a 7.5 × 11.25 arc-second (250 m) grid, was utilized for precisely applying terrain correction to the regional gravity field model. Consequently, we created a gravimetric geoid model for Japan, consistent with 971 GNSS/leveling geoid heights distributed over the four main islands of Japan with a standard deviation of 5.7 cm, showing a considerable improvement by 2.3 cm over the previous model (JGEOID2008). However, there remain some areas with large discrepancies between the computed and GNSS/leveling geoid heights in northern Japan (Hokkaido), mountainous areas in central Japan, and some coastal regions. Since terrestrial gravity data are especially sparse in these areas, we speculated that the largeness of the geoid discrepancies there could be partly attributed to the insufficient coverage and accuracy of gravity data. The Geospatial Information Authority of Japan has started airborne gravity surveys to be covered over the Japanese Islands, and in future, we plan to develop a geoid model for Japan further accurately by incorporating airborne gravity data to come.
