The Influence of Reference System Disparity on Navigation and Positioning,
DEFENSE MAPPING SCHOOL FORT BELVOIR VA DEPT OF TOPOGRAPHIC SCIENCES
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There are many geodetic datums in use throughout the world today. Each of these datums serves as a reference surface for the mapping, charting, and geodetic work done in a specific geographical area. Each datum is defined by fitting a specific ellipsoid to the earth in such a manner as to minimize departures of this reference model from the geoid over the area of concern. Historically, these datumshave been relatively oriented. Consequently the position of the center of an ellipsoidal model relative to the center of the mass of the earth is not known. The positions determined on one datum cannot be related accurately to positions on another datum. The development of absolutely-oriented datums incorporating satellite and gravity data has led to the development of datum transformations to relate positions on one datum to those on another. Sophisticated new electronic navigation and targeting technology requires highly precise input data to obtain output on the order of design accuracies. To obtain positions on the order of - 1000 feet, care should be taken by the users of such equipment that the datum to which positions are referred is taken into account.