separations will occur. For this reason, and because the ties between local triangulation in southeast
Asia are typically weak, the India datum is probably the least satisfactory of the preferred datums.
1-16. Deficiencies. The preferred datums, though an improvement over the older national datums, have
serious deficiencies. The effect of these deficiencies is that the preferred systems do not provide the
geodetic information required for intercontinental-range missiles. It is true that the HIRAN North
Atlantic tie permits connecting the European Datum and the North American Datum. However, this
does not completely solve the problem, for both the North American and European Datums are relative
(Figure 1-24). While in each case the ellipsoid chosen is an adequate fit in the area of the origin, neither
provides a good fit for the entire earth. Also, the process of connecting various datums by means of
intervening datums or triangulation ties allows for errors and does not always provide agreement with
newly observed data. The surveys joining India to the European and the Tokyo Datums also present
such a problem. Since the preferred datums are relative and the few existing connections between the
preferred datums provide weak ties, it is not possible to compute geodetic distances and directions
between the systems, and the requirement for long-range geodetic information is still unsolved.
Figure 1-24. The Preferred Datums are Relative Datums
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EN0593
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