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Figure 7: The World's Major Datum Blocks.
Figure 8: Shows the multiplicity of Astro-geodetic datums in the Indonesian Archipelago.
A global datum is a datum that is established to model the entire global geoid as closely as possible; something an astro- geodetic datum cannot do. A global is datum is established by observing the orbit of navigation satellites, calculating the E h’s centre of mass based on the orbits and then adjusting the ellipsoid by harmonic analysis to fit the global geoid. There have been several variants, but the two primary ones are WGS 72 and WGS 84. WGS stands for World Geodetic System. The WGS 72 datum was establ sh d fo h ‘ ns oppl ’ s ll sys m, WG 84 w s s bl sh d fo h G sys m. h ‘conn c on’ po n o o g n for the global datums is the E h’s centre of mass. Due to iterative improvement of the gravitational analysis, the centre of mass is slightly different for WGS 72 and WGS 84.
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